Meghan Markle certainly knows how to impress the in-laws. She has announced that she and Prince Harry are going to devote much of their married life to the Commonwealth. And we all know how much the Commonwealth means to the Head of the Commonwealth. In this week’s interview to mark their engagement, the future princess mentioned it twice as she spoke of her ‘passion’ for all the ‘young people running around the Commonwealth’. The Prince himself is already plugged in to umpteen charities on this patch, not least the excellent Queen’s Young Leaders programme. It is all music to the ears of a monarch who, as a young princess herself, famously pledged ‘my whole life, whether it be long or short’ to this ‘family of nations’.

The Commonwealth badly needs a boost. It should have been all over the news throughout the fall of Robert Mugabe; it is perfectly placed to help rebuild that troubled nation. Yet, aside from a throwaway line from Boris Johnson, we have barely heard any mention at all. Sometimes it seems that the FCO has dropped the C. Harry and Meghan can now do wonders for its profile. No wonder the Queen and her corgis have taken a shine to the new girl. Imagine if she turned to be good with a horse, too.

Two golden rules of royal weddings. First, it’s always wonderful on the day. Second, there is always an almighty official spat beforehand which no one saw coming. When Prince Charles married Lady Diana Spencer, there was a Spanish boycott because the honeymoon included Gibraltar. In 2011, Prince William’s marriage plans had a crisis moment when it turned out the guest list had included the Syrian ambassador but not ex-PMs Blair and Brown.

We can already spot one sensitive issue. Should Donald Trump be invited? For: the bride is American. Against: she backed Hillary. In fact, Mr Trump is unlikely to be invited because he is not a friend and this is not a state occasion. Prince Harry is only fifth in line to the throne and falls further with each new royal arrival at the Lindo Wing.

But don’t rule out a presidential presence. Prince Harry’s greatest achievement is his Invictus Games. Two great supporters have been the previous occupants of the White House. It may displease the Donald, but look out for the Obamas at St George’s Chapel.

That an engagement between a royal prince and an American divorcee is so uncontentious these days is, in part, down to way society has changed since the micro-reign of Edward VIII. But it is also down to a piece of coalition legislation of which David Cameron and Nick Clegg are still very proud. This will be the first royal marriage since the Succession to the Crown Act of 2013 which ended male primogeniture and the bar on marrying Catholics. It has also served to ‘normalise’ royal marriage — in as much as there is anything ‘normal’ about a wedding with commemorative mugs, tea towels and a global TV audience. So will there be invitations for the Camerons and Cleggs?

Jeremy Corbyn’s response to the engagement was warm and gracious. ‘I hope they have great fun together,’ he told a Labour gathering, ‘and having met Harry, they are going to have a great deal of fun.’ But many Corbyn supporters booed the media for even raising the issue. Of course, it wouldn’t be a royal wedding without a republican strop. On the day Charles married Lady Diana, a band of Labour firebrands organised a cross-Channel away-day to escape the ‘royalist orgy’. The ringleaders were Harriet Harman and Peter Mandelson.

I was sad to read of the death of Bill Pitt, victor of the first by-election I watched on television. His 1981 win for the Liberal/SDP Alliance in Croydon North West might have been historic, but it is the celebrations which stick in the mind. As a supporter sprayed him with champagne, Grand Prix-style, Pitt was incensed, shouting: ‘My new suit!’ By chance, I met him on the 2015 election trail at a meeting in Kent where he was campaigning for Labour. I had to ask him about his champagne moment. ‘Everyone remembers it,’ he laughed. ‘And, do you know, I’ve still got the suit!’