Holding a tray groaning with slabs of lemon drizzle and carrot cake, Rishi Sunak admitted that the toll of the election campaign had caused him to break his discipline of fasting every Monday. “That’s out the window,” the prime minister joked on his first day back on the campaign trail after being forced to apologise for missing a crucial part of the D-day commemorations. He was surviving on pure sugar now, he said, stashing bags of Haribo Tangfastics and giant chocolate buttons on the Conservative battlebus. This is about as close to a bender as the fastidiously health conscious prime minister gets. He emerged into the light on Monday, smiling in a zip-up green fleece, but he was not yet ready to venture into hostile territory. The venue for his first campaign visit back on board the battlebus was a garden centre in Horsham for a coffee among hanging baskets filled with pansies. It should be the deepest of blue territory – a West Sussex seat with a Conservative majority of more than 21,000 and a highly ambitious 68th on the Liberal Democrats’ target list. It’s a sign of the Conservatives’ dire standing in the polls that Sunak felt the need to come here on Monday. His presence barely seemed to trouble the pensioners having cooked breakfasts in the garden centre cafe. There was a new humbled tone to his answers about his blunder in leaving the commemorations in Normandy before the main international event, ostensibly to return in time to do an ITV interview – though aides have stressed it was agreed in advance that he would leave after the British event. He made no excuses, nor asked to draw a line under the matter, but asked if “people can find it in their hearts to forgive me”. Earlier in the morning, Sunak had been knocking on doors in Crawley, normally a key bellwether seat and one which Labour should take at a canter if the polls are right. Tellingly, no cameras were there for that part of the campaign. In Horsham, Sunak steeled himself for a barrage of questions from reporters on his political future – including if he would survive to the end of the campaign. Even he could not bring himself to say that he was finding voters who were sticking with his party, only that voters he had met in the morning were “recognising and accepting that we are the party that have put forward big ideas”. He said, in hope perhaps rather than expectation, that would transform into people coming out to back him again. “That’s why I’m talking to people every day,” he said. It was a tacit admission that shoring up the core vote is a key priority. Sunak brushed off questions about the polls – which have not moved in the two weeks since the election was called – saying he had been “written off” since he took the job after Liz Truss’s downfall and that the election was not a “foregone conclusion”. In a message perhaps directed more at his weary or mutinous troops, he said he was “not going to stop fighting”. The next stop was the Dog and Bacon pub, decked out in St George’s flags ready for this week’s Euros, for a brief stop to meet the local Neighbourhood Watch to speak about his pledge to recruit 8,000 new police officers. Half an hour later, he was out again, with public campaigning all concluded by 10.30am. He declined the battlebus back to London in favour of a private car.