After months of political intrigue, bruising byelections and feverish planning from Manchester to Westminster, sometimes the power of a big moment is better illustrated in a simple act. In this instance, it was a hug from a tearful mum, proud of her boy on his big day.Just before Andy Burnham walked into Number 10 for the first time as UK prime minister on Monday lunchtime, he moved along a line of people who had gathered behind him on Downing Street to clap and cheer him on.He paused in front of a lady, resplendent in the summer sunshine in her bright-white blazer over black blouse. It was Eileen Burnham, the new prime minister’s mother. Their embrace was lasting and tender, the emotion creased across both their faces.Burnham credits his parents, and in particular his mother, for seeding his personal ambition and also for imbuing him with the strong values he says drives his politics.She also gave Burnham his religion as a baptised Catholic, which he says helped shape his political outlook on issues such as the duty to combat poverty.New UK prime minister Andy Burnham embraces his mother Eileen. Photograph: Oli Scarff/AFP via Getty Images Now he was the UK Labour Party’s first Catholic prime minister. Eileen Burnham’s boy had done good. All he’d ever wanted was to be leader of Britain. Now, as he took office with lofty promises to end rough sleeping and build social care, he had to govern it.“Let us make this the moment when Britain starts to believe again, the moment we bring back hope,” he said before walking through the black door.Burnham’s first hope had better be that he fares better in the role than his litany of short-lived predecessors.Earlier, before the final goodbyes of the ousted Keir Starmer from outside Number 10, Downing Street had been a hive of activity. Broadcasters had spent the weekend marking with tape coveted positions on the street, the best camera angles to witness the end of one man’s political journey and the beginning of a new era under another.The street was full by 8.30am, its hastily-rigged broadcast platforms heaving beneath the weight of journalists from across the world delivering pieces-to-camera.The omnipresent patchwork of protesters of various hues that usually congregates at the bottom of Downing Street had been pushed back a little. There was also no sign of Steve Bray, the music-blaring anti-Brexit campaigner whose aural interludes were the soundtrack to every UK prime ministerial change since Boris Johnson’s 2022 exit.This time, London’s Metropolitan Police had decided to enforce temporary regulations banning the use of amplifiers on Whitehall. Starmer’s speech last month announcing that he intended to step down had been marred by loud music. On Monday, as he finally quit, he would be afforded a little more dignity.Choppers began to swirl overhead at about 10.30am as the big news networks anticipated Starmer’s drive to Buckingham Palace, where he would ask Britain’s king Charles to accept his resignation and recommend that Burnham replace him.At about the same time, junior government figures entered Number 10, including James Timpson, a businessman-turned prisons minister, and Patrick Vallance, the UK government’s chief medical adviser during Covid who later became a science minister.Both men had just quit the government before Burnham took over, thereby avoiding a purge of Starmer loyalists – that was to follow later. Now, they had arrived to say goodbye to their leader as his time neared an end.The famous, well-used Downing Street lectern was pulled out on to the cobblestones at about 11am. Political staff soon streamed out the doors of Number 11, the office and home of the chancellor of the exchequer, and Number 10 next door.Outgoing prime minister Keir Starmer and Rachel Reeves. Photograph: Peter Nicholls/ AFP via Getty Images They were soon joined by a large group of senior Labour political figures, including deputy prime minister David Lammy, chancellor Rachel Reeves and housing secretary Steve Reed. Starmer loyalists, all would be sacked by Burnham before the day was out.The staff and politicians all gathered outside the door waiting for the exiting PM. Many of them were wearing shades to combat the glaring sunshine. In their suits and dark glasses, they looked a bit like a gospel choir, or a convention of Blues Brothers fans.Starmer eventually emerged from Downing Street at 11.15am, which was the precise time suggested by Number 10 staff several days previously – the outgoing prime minister was reliably managerial, right to the final minute.Less emotional this time than he had been last month when announcing he was quitting, Starmer focused on his legacy, highlighting his achievements since entering office: “I am confident that Britain is now stronger and fairer than it was two years ago.”He spoke about cutting NHS waiting lists, helping Ukraine in its war with Russia, cutting immigration. “So, as I now pass the baton to Andy Burnham, I wish him every success. He has my full support,” said Starmer.He appeared to seek out Reeves in the crowd to give her a hug before he left, perhaps a portent of the fate that he knew awaited her later on. Then he swept out the back gates of Downing Street to Buckingham Palace as a new era dawned.A different crowd of well-wishers – friends, family and backers of Burnham – streamed out the doors of Number 10 and Number 11 just over an hour later, as news emerged that the new man had also been to see the king and was now the prime minister.A lone voice, coming from behind Downing Street on Horse Guards Parade, shouted loudly over and over again in a football chant: “There’s only one Andy Burnham.”Then he arrived.Andy Burnham, UK prime minister, speaks outside 10 Downing Street. Photograph: Chris J Ratcliffe/Bloomberg Burnham chose not to stand behind a lectern, channelling a more relaxed style as he spoke. He said his generation of politicians had “not been good enough”. He said they needed to raise their game and “rise to the new challenge”.He suggested that he would try to eschew the economic and political orthodoxies of the previous four decades in Britain, and seek out something new.“In the 1980s, Britain took some wrong turns . . . We will change politics to make it more collaborative, more about problem solving than point scoring,” said Burnham.“Britain needs to show the world that we can regain our stability once again and that is our challenge – to make politics work, to make it work better.”Burnham announced that his first order as prime minister would be to find solutions to end rough sleeping. He also promised the British people that he would try to find ways to ease the cost of living. He also said he would soon outline ways to pay for it all.“We will make this moment a circuit breaker for Britain, bringing forward the biggest changes in the last 40 years,“ said the new prime minister. ”A new political model and a new economic model . . . Later this year, I will bring forward a new plan for Britain, a 10-year plan."The old prime minister once spoke about his own 10-year plan. But now, two years later, he was on his way to the political wilderness as a new era began.Life comes at you fast in Downing Street, as Burnham will soon know better than anyone.[ Burnham becomes British prime minister: as it happenedOpens in new window ]