They are supposed to be the dream team who can solve the conundrum of how to win the election. But David Cameron and Boris Johnson were left scratching their heads today as they struggled with a children's jigsaw teaching toddlers about the seasons. As the London Mayor tried to hammer ill-fitting pieces together with his hands, the Prime Minister tried out what could be a new election slogan, telling him: 'If in doubt, wedge it in.' After being put right by a four-year-old who spotted their errors, the pair had more fun finger painting with Tory blue paint. David Cameron and Boris Johnson were left stumped by the puzzle at Advantage Children's Day Nursery in Surbiton, as three-year-old Stephanie looked on . When they tried to put the puzzle back together, they hit trouble after it proved to be more difficult than expected . The Conservative duo made their first appearance together on the campaign trail with a visit to Advantage day nursery in Surbiton, south west London. They were supposed to be highlighting Tory plans to double free childcare for 600,000 children aged three and four. They sat at a table with Joshua and Stephanie, both aged three, and four-year-olds Hamish and Leo where they broke up a puzzle which depicted the four seasons. When they tried to put it back together, they hit trouble after it proved to be more difficult than expected. After taking nine minutes to complete the puzzle, the Tory duo were relieved to try their hand at hand painting, which they found much easier . The pair were at the nursery in Surbiton to promote a Tory pledge to double free childcare for working parents of three and four-year-olds to 30 hours a week . Arriving at the nursery, Mr Cameron appeared to be giving Mr Johnson a ticking off before the visit had even started . Like a bad workman blaming his tools, Mr Johnson soon started to question whether there was a fundamental design fault. 'January is in winter,' he complained. 'There's something wrong with the puzzle.' The clock ticked on and Tory aides grew nervous, as Mr Cameron insisted: We've got all day.' Mr Johnson, fearing defeat, was adamant: 'We can't be beaten by the puzzle.' With the media crowding into classroom, Hamish asked Mr Cameron why there were so many journalists. 'If we finish the puzzle it will make them go away,' the PM said. But the children had spotted more errors. 'I've found another problem,' said Leo. Mr Johnson, already known as a political heavyweight, then tried brute force to get the pieces to fit by hammering them with his fist. He had the backing of the PM who declared: 'If in doubt, wedge it in.' Samantha Cameron got into less mess with blue paint during a visit to The Growing Zone allotment project in Kippax, West Yorkshire . Fearing it might be taking too long, and perhaps that the puzzle might get broken, a teacher then stepped in to point out yet more problems. 'This one is not right,' she said. 'This one goes there.' As the last piece went in to cheers - nearly nine minutes after they began - Mr Cameron initiated a group hug. 'Thank God for that. That was stressful,' he said. 'I do have to have a hug after that.' Mr Johnson joked: 'That was a bit like the (election) campaign ... suddenly, the final surge.' 'It all comes together in the end,' said Mr Cameron, before stopping one of the children taking the puzzle to pieces. 'Don't break it up again - I can't take the stress.' Afterwards the two men joined another group of children for a hand painting session - appropriately using blue paint.
David Cameron and Boris Johnson visit nursery to promote childcare .
Duo left flummoxed by jigsaw aimed at teaching children about seasons .
London Mayor resorted to brute force to hammer wrong pieces together .
Prime Minister gave his approval, telling Boris:  'If in doubt, wedge it in'