Prince Harry Catherine and Prince William
Prince Harry, Catherine, Duchess of Cambridge and Prince William, Duke of Cambridge speak during the launch of the Heads Together campaign on mental health on 16 May 2016 in London. Getty

At the recent BT Sport Industry Awards dinner in London, the spectacularly tiny and charming Kevin Baker, CEO of luxury goods firm Thomas Lyte, had some news he wished to share with me. It was news so exciting that he felt compelled to whisper: "The Queen has granted us a Royal Warrant as goldsmith and silversmith."

The lifelong republican in me – albeit one who admires the Queen sufficient to put her in my recent book,Winners: And How They Succeed, as a peculiarly Great British winner – rose up. "Why do you care so much?" I said in anything but a whisper. And he told me: because it was good for his business and because it made him proud to be British.

A few days later I was at one of the several events I did for Mental Health Awareness Week, and also there was Paul Farmer, the brilliant chief executive of the equally brilliant Mind. One of his team sidled up to me – she was another whisperer – and said:

"You might want to congratulate Paul on his CBE." No, no, no, the republican in me raged again.

Loudly I went into my pantomime honours system denunciation mode, but I could tell that the listening gaggle felt I was the one out of step with fashion and opinion, while Paul was right to be feeling proud of this particularly British form of recognition, via membership of an empire that no longer exists.

The anti-elitist in me will always think that the honours system is one of the establishment's tactical levers that always ensures, whatever changes of government and culture there may be, that the basic class structure of the UK does not change. We are a less elitist country than we were. But just take a look at the make up of our cabinet, our civil service, our media, our top businesses, analyse their birth and schooling, and ask yourself if we can truly claim to be a meritocracy where background matters less than talent and hard work.

However, as I acknowledge in the chapter on the Queen in Winners, as I near my seventh decade, and she enters her tenth, she has seen us off, certainly for my lifetime, and well beyond. Fair play to her.

But as the republican in me admits defeat, this opens up the space for another part of me – the mental-health campaigner – to welcome this continuing British and indeed global obsession with all things UK royal. Because one of the highlights of Mental Health Awareness Week was the involvement of the younger royals, Prince William focusing on the need for men to be more open about their mental health, Prince Harry following on from his brilliant Invictus Games involvement with a call for more to be done for military veterans with mental health problems, and Kate highlighting the importance of better understanding and treatment for children with mental health problems.

The republican in me wants to say why on earth should these people be able to influence the agenda in the way they do? But the mental-health campaigner in me rejoices and thinks it is brilliant that of all the competing causes, charities and campaigns that fight for their attention, they have gone for this one. It has an impact in terms of their ability to generate media coverage, which is important to a campaign that is so much about breaking down stigma and taboo. The mere fact of them talking about it so much helps to strip away the stigma. That in turn has a indiscernible but – believe me, from my government days, I know – undeniable impact upon the priorities, the deliberations and the decisions of policy-makers.

Of course, it has to be real and authentic for the weight they add to be of any lasting value. The clear sense of those who have worked with them in developing their campaigns is that it is. I know, for example, of private visits they have made to some of the lesser-known service providers in order to better inform themselves. I don't think anyone who saw Harry's interaction with the Invictus veterans, or the passion of his speech at the closing ceremony, could fail to see that for him the cause of injured soldiers is real.

By dint of their status as future king and queen, and perhaps also a difference in personality, the style and language may be different from William and Kate, but of them too the strong sense is that this is a campaign of real weight and one that would be enduring. That is very good news for those of us who want to see a step change in attitudes to mental health and mental illness, and one day a tipping point from which we look back and say "Why did it take us so long?"

Here is the other thing that makes me happy about their input. The monarchy is almost by definition a deeply conservative institution. It adapts and changes slowly. The Queen in particular is not fond of dramatic steps or gestures. So when they alight upon a cause, and seek to use their influence to advance it, they want to be sure they are working within or at least close to the mainstream of public and political opinion. That they choose to become so passionate and so high profile about mental health is not merely a driver of important steps forward. It is a major indicator of steps already taken within our culture and our society.

We are still a long way from being able to say that the equality between physical and mental health –which is set out in the NHS Constitution, no less – exists in reality. Indeed, as I said to two separate Mental Health Awareness Week events recently – one at Barclays, the other at Channel 4 – I worry that as we strip down the walls of stigma so that more and more people come forward in the belief that they need medical support, they may find that the services are not there.

But as the fight goes on, when I ask myself, republican or not, if I would prefer to have the Royals on that side of the mental health debate that calls for more openness, more awareness, less discrimination, better understanding and less discrimination, I don't need to think about the answer for long.

Alastair Campbell is a writer and strategist, best known for his work as Director of Communications and Strategy for Prime Minister Tony Blair. He is an ambassador for Time to Change and Alcohol Concern and a patron of the MayTree suicide sanctuary in North London.