Pope's funeral an opportunity for world leaders to do more than pay their respects - the PM was always bound to go

Sir Keir Starmer says he doesn't believe in God and US President Donald Trump rarely speaks of religion.

But both will attend the Pope's funeral. After all, Catholics are the second biggest religious group in both countries, with six million in the UK and more than 50 million in the US.

Here in the UK, regular church going is reported to be up from 8% to 12%, while the US president said after Pope Francis's death "we're bringing religion back" to America. Pope dies latest - funeral details announced Politicians - and indeed church leaders - take note.

Yet Catholics are relatively under-represented in the House of Commons, even more so after last year's Labour landslide when several prominent Catholic Tories were defeated. Surprisingly, Boris Johnson was the UK's first Catholic prime minister, converting after almost two years in Number 10 before marrying his Catholic bride, Carrie Symonds.

Tony Blair, who in his early life was a Durham Cathedral chorister, became a Catholic after leaving Downing Street. His wife Cherie is Catholic.

That was despite his spin doctor Alastair Campbell notoriously telling an interviewer who asked about Mr Blair's faith: "We don't do God." Gordon Brown was famously a "son of the manse" - his father was a Presbyterian minister - and Theresa May's father was a Church of England vicar. Another former prime minister, David Cameron, on the other hand, rather irreverently once described his faith as coming and going "like Magic FM in the Chilterns".

But despite Sir Keir regularly being described as an atheist, two senior members of his cabinet, Education Secretary Bridget Phillipson and Cabinet Office minister Pat McFadden, are Catholics. "For me, being Catholic has always been about a wider sense of social justice, social action, the value and worth of every individual," Ms Phillipson has said, though she added: "I part company on issues around abortion, contraception…" Mr McFadden, the son of Irish Catholic parents, paid tribute to the Pope after his death: "Pope Francis served until the very end, including this Easter time.

May God rest his soul." The most openly religious senior Labour minister is the foreign secretary, David Lammy, who has said Jesus Christ was the inspiration for his politics as well as his lifelong faith. Rachel Reeves and Wes Streeting are practising Anglicans, Jonathan Reynolds chairs a group called Christians on the Left, and Stephen Timms is an evangelical Christian.

Among the Conservatives, last year's crushing defeat saw several senior Catholic Tories, including serving and former cabinet ministers, lose their seats. The casualties included cabinet ministers Gillian Keegan, Mark Harper, Therese Coffey, Liam Fox, Damian Green and Jacob Rees-Mogg, along with junior ministers Maria Caulfield and Paul Maynard and senior backbenchers Damian Collins and Daniel Kawczynski.

That leaves just the Father of the House Sir Edward Leigh, former party leader Sir Iain Duncan Smith, and former cabinet minister Damian Hinds as the only remaining senior Tory Catholics left in the Commons. Backbencher Danny Kruger, who is leading the fight against the controversial assisted dying legislation, the Terminally Ill Adults (End of Life) Bill, says he's an evangelical Christian.

For world leaders like Sir Keir and Mr Trump, however, attending funerals of world statesmen or the great and the good is about more than paying their respects. They are an opportunity for official or unofficial meetings with other world leaders, known in the jargon of international diplomacy as a 'bilateral', a 'brush-by' or a 'walk-and-talk'.

So expect plenty of these on Saturday. Read more:Is the Conclave movie accurate?Pope Francis: A life in picturesFrancis was a champion of the deprivedInside Vatican City at moment of high tension After all, besides Sir Keir and the US president, the leaders of France, Germany, Brazil, Argentina, Poland, the European Commission and indeed Ukraine's President Zelenskyy have already announced they're going.

It could be one of the biggest gatherings of world leaders outside an official G7, G20, EU or other international summit. So, of course, Sir Keir and President Trump will be there..