Prince Harry's wedding to Suits actress Meghan Markle will be the wedding of the year in May 2018, as he shakes up the monarchy with his modern romance.

As the world prepares to cast their eyes on the bride and groom on their big day just five months away, speculation is rife about how much it will cost the Royal household, who have pledged to pay for it.

Kensington Palace announced that the Queen had granted permission for her grandson Harry to marry divorcee Markle, who was married to Trevor Engelson between 2011-2013, and that the Royal family would fund the wedding.

A statement read: "The Royal family will pay for the wedding," which is set to take place in St George's Chapel at Windsor Castle. It added: ''Further details about the wedding will be announced in due course."

Hamish Shephard, the founder of wedding planning website and app, has made his financial predictions about the royal wedding.

He told IBTimes UK: "Whilst every wedding is expensive, with the mix of royalty, Hollywood and global attention, Harry and Meghan's will no doubt be the global wedding of the year."

"With such a price tag, Meghan's family can thankfully breathe easy as the Royal family are generously paying for the whole occasion.

Shops, hotels and even West End theatres can expect a boost of up to £2bn from the Royal wedding of Prince Harry to American actress Meghan Markle
Shops, hotels and even West End theatres can expect a boost of up to £2bn from the Royal wedding of Prince Harry to American actress Meghan Markle Reuters

"A beautiful American actress marrying a caring British Prince in a royal castle could easily be a fairytale in itself, so the whole world will be watching and wishing them well."

"The cost of a marriage at a Registry Office in the UK is £46, so at 32,000 times the cost, this is clearly is going to be an incredible occasion!"

In terms of actual figures, Shepard expects the big day to set the Royal family back approximately £1.5m, and that's not including the £10m security costs.

He said: ''Meghan and Harry's wedding is expected to cost £1,463,273 ($1,964,312 USD), and that's not including the honeymoon or the £10 milllion expected security costs involved on top. Their wedding will cost almost 100 times the average cost of a wedding.

''Their highest expenditures are likely to be the catering, drinks and the decor.''

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Shepard went on to compare the royal wedding to the average one in Britain. He said: ''Today's couple spends an average of £16,842, and the average wedding size is 78 guests for the ceremony and 83 guests for the evening.

''In comparison, 1,900 people attended the ceremony in Westminster Abbey for Prince William and Kate, with a second list of approximately 600 then being invited to the reception at Buckingham Palace.'' predicts Harry and Meghan will choose to have a relatively small celebration, by Royal standards, with only 800 people at the ceremony and formal lunch time reception, followed by a private evening reception for only the closest family and friends of about 300 people.

Many are speculating a more relaxed tone, compared to previous royal ceremonies. In fact, Harry and Markle have said they'd like the public to be involved.

Shepard cites that the floristry will cost £110K and the drinks £150K alone.

Meghan Markle meets adoring fans on first official royal engagement Reuters