The long wooden benches and looming balconies of the City of London's St Botolph's-without-Bishopsgate are full on this dim December lunchtime.
There's a school choir and band on the stage at the front of the fine 18th Century building, which has roots dating back to the Anglo-Saxons, while three ornate chandeliers hang above the heads of the congregation for this year's carol service, the warm glow of the light belying winter's cold chill outside.
Wide mouthed and full lunged, the Christian revellers bellow impassioned verses of well-known Christmas carols, such as Good King Wenceslas and Hark! The Herald Angels Sing, singing the praises of their god and listening intently to the moral lessons during readings in between.
Among this crowd of the faithful are suited professionals from the City of London, the beating heart of the global financial world and a place where in recent years it seems the Seven Deadly Sins have been more of a CV requirement than moral code, with tales of greed, lust and wrath involving those who work within its sky-scraping money temples.
"Our financial professionals who come to church, they're not devils," says the Reverend Dr Alan McCormack of St Botolph's, as we sit in his office wood-panelled office at the back of his church after the busy service.
"They're not different, really, than we are. They just happen to be doing that kind of job.
"I think any job that we do ... you can get carried away in your own bubble. You just get trapped.
"Really, from a Christian point of view, as I would see it, what banks are most in need of is a discourse of trust and value.
"That's really what the difference is between someone who can exploit a financial situation and someone who will not exploit a situation even though she could."
Trust, it is fair to say, is not something the public have in banks.
The financial crisis, catalysed by the irresponsibility of bankers in the US who sold toxic derivatives linked to sub-prime mortgages, has plunged the world into an economic downturn.
This in itself, as Western populations lick the wounds inflicted by government austerity cuts as they struggle to put food on the table, is enough to have dissolved public trust in the financial world.
However, since the crisis there has been revelation after revelation about the grubbiness of an industry now desperately trying to scrub the dirt away.
From attempts to fix interest rates such as Libor, to the compensation doled out in penance for the endemic mis-selling of financial products such as Payment Protection Insurance on loans, to money laundering on behalf of rapacious criminal gangs and murderous terrorists, the financial sector has a full house when it comes to scumbag bingo.
How, then, do finance workers who consider themselves Christian square the circle of being part of an industry that has seen so much moral and ethical corruption? How do they feel they can work as part of an industry that is driven primarily by the need to make money, often with no real care for where that profit is derived?
For example, a boss at commodities trader Glencore was criticised when he said the firm would benefit from a food crisis, something that has seen millions of people taken into the deathly grip of famine.
"The environment is a good one. High prices, lots of volatility, a lot of dislocation, tightness, a lot of arbitrage opportunities," said Chris Mahoney, Glencore's director of agriculture trading.
"Having worked for the banking industry for many years then I'm supporting an industry which does that sort of thing," says Alastair Harris, a Christian operational risk and control manager who has worked for some of the City's most well-known investment banks.
"How do I square that off? Because we have a means of exchange of scarce resources, such as money, not just food, doesn't preclude the needy and the hungry.
"In fact, I can be an instrument to actually promote that within. I don't think it's an answer to say that I'm not going to have anything to do with this because it's totally immoral, because it's not. It's shades of grey.
"When you're in an environment with shades of grey I don't think it's good enough to actually say I'm not going to take part in it, because you end up not taking part in anything.
"It's a bit like anarchists who say 'I'm against capitalism so I'm not going to take part in it'. Unless you go and live on a Scottish island with no electricity, no interface with the outside world, you will have to compromise in some say.
"For me, it's actually about making the place more human and being an instrument, being a tool, an agent, whatever. You can't do hear no evil, see no evil, speak no evil.
"No doubt there are plenty of organisations who are doing things that detriment the poor, and if I see those and know about them then I will do something, but I don't think it would be to withdraw myself. I'd rather try and influence people."
Parable of the Talents
God, if we are to believe the bible, is not a big fan of banking.
To take just one of many examples, Deuteronomy 23:19 explicitly states that loans must not have any interest charged on them.
But that's so Old Testament and the sequel is kinder to financiers.
Jesus Christ essentially laid the foundations for interest rate swaps and other derivatives products, of the type banks are being fined billions for mis-selling, in his parable of the talents.
In this parable a master leaves his money with three servants before hopping on a donkey and heading on his travels. When he comes back, two of them have invested the money and made a return.
The third buried his cash so he didn't lose any. He hands over the cash when his master arrives home, only to be given a stern telling off for not investing it with bankers instead so he could have made a profit through interest.
Indeed, the servant would have been wise to put the money into some kind of biblical derivative, like a bond linked to an index for bread and fish production, an industry whose output rose sharply thanks to a divine intervention from Jesus himself.
"Throw out the unprofitable servant into the outer darkness," howled the master, a surprisingly angry, greedy and unforgiving man to be held up as an example of virtue by Christ, "where there will be weeping and gnashing of teeth."
'It's competition just like any other industry'
John Philips, a retired investment analyst in European food manufacturing equities, who also worked for one of the world's biggest banks, said he is "aware that there is a mass of hostility at the moment" towards the financial sector.
"I was at the National Theatre a couple of nights ago and there was some passing reference to bankers in a disparaging way and the audience practically stood up and gave the actor a standing ovation, which I think is silly," Philips says in a quiet corner of the bustling church.
"There's nothing immoral about lending people money, I don't think, and I don't see any biblical basis that there is. Most people operating in markets, be they currency, shares, bonds, portfolios or whatever, are almost intermediaries.
"My personal role was an advisory one, so I wasn't taking decisions about which shares to buy or which shares to sell, I was advising someone.
"The professional investor who I was advising was paid to make the best investments he possibly could on behalf of those people whose money had been entrusted to him, be it pension funds or others.
"It's competition just like any other industry. You try to make the best cars and sell as many as you can, you might say what do you think about putting weaker car companies out of business?
"In competition that's what happens, so I don't see a moral issue in investing in anything.
"Well tobacco, perhaps."
Reverend McCormack pointed to the City of London's investment fund Arcubus as an example of responsible finance with a Christian foundation.
Arcubus issues bonds with decent returns, according to its website as much as 10 percent on your original investment, and the money is used for international development in some of the most desperate places on earth through microfinance initiatives.
"Uniquely, it offers an effective way for City workers and companies to take action to support some of the world's poorest communities, whilst also building their own future markets," says the website.
"I'm sure there are many other cases where it doesn't come from a Christian background, but it is still nevertheless, in terms of a Christian analysis, a good thing to do," says Rev McCormack.
Both Harris and Philips say ethical and moral dilemmas for working Christians are not exclusive to the financial industry.
"I think that as a Christian in any environment there is always a challenge," says Harris.
"It doesn't matter if it's banking, or agriculture, or law, or whatever it is. I think there is always a challenge to try and remember one's values and try and stick to them without damaging relationships."
At the moment Harris, who is a director of a limited company through which he works as a contractor, is juggling with the morality of his tax arrangements.
As with many freelancers, Harris is paid through his company and his income is derived through dividends. This is more tax effective than simply receiving payments for work directly and paying income tax.
"I think the problem with it is that the taxpayer is partly paying for my risk, because the tax rates are lower," Harris says.
"I should be remunerated for higher risk, yes. Risk:reward ratio, certainly.
"Part of the way it's working is banks are taking advantage of the fact that I can have a limited company, pay lower tax, and the banks don't actually have to pay as much. I think there's a moral issue there.
"In the current circumstances I feel quite uneasy about that, I have to say. Why should I pay less tax?
"But then of course, you would argue it's totally legal. There's nothing illegal about it."
The moral obligation on tax, he posits, perhaps lies with legislators, but it is an issue he is still thinking about.
Can Christianity play a part in banking reforms?
Finance is going through a period of structural reform, with new regulations and regulators set to take hold of the industry.
Outside of the debate on the technical side of the banking world - from ring fencing to remuneration - there is also discussion on the theme of culture and ethics.
Perhaps, as Christians, they feel their faith and its core values could influence the cultural reforms that are so desperately needed in the financial sector?
"Everybody has something to learn, from my view, in Christianity - bankers included," says Philips.
"The fundamental idea of Christianity is that you treat people decently and don't try to cheat them, and that could apply in any area of business."
Harris says his own role in risk management could be seen in itself "as trying to safeguard the organisation and protect it from wrongdoing".
He also points out that there are many bankers who are devout Christians and in senior positions who could have made changes to how things worked and the practices of their businesses.
"I think that goes to demonstrate that there are people out there, Christians, up to their necks as much as anybody else," says Harris.
"At the end of the day, my faith is a very personal thing. It's how I interact with who I consider to be my maker and how I interact with other people.
"As much as anything, it's the effect on me and individuals that's important, and how we learn."
Rev McCormack says finance could, from a Christian's perspective, be godly.
"The first point about Christianity, and certainly when we celebrate something like Christmas and the meaning of Christmas, is that god becomes part of the world, god transforms the world.
"So there is no part of the creation that does not have the capacity for god to be part of it. Finance can certainly be part of that.
"The other point of Christianity, and again it comes out of the idea of Christmas incarnation god changing the world, is that in Christianity we don't have a faith that does not develop.
"Not quite compromise with the context within which it is finding itself, but participating in that context for a transformational purpose.
"Therefore, it would be true to say that banking, finance, law, the media - none of these things lack the capacity for god and the things of god to be involved with them. But the things of god being involved with them ought to lead to a difference in practice."
He says he has been part of efforts by the Lord Mayor of London, David Wootton, to have a "discourse on trust and values" in the City.
He has been to meetings and discussions on this topic at Mansion House, the Lord Mayor's 'office' if you like, with "the biggest wealth creators and wealth destroyers in the City".
"For me, the spectacle of a room that included the CEO of Deutsche Bank and the Archbishop of Westminster - it's not what you would think," he says.
"But the fact that it's happening, you might say, is cosmetic, or you might say something is changing."