By . Matt Chorley, Mailonline Political Editor . PUBLISHED: . 09:40 EST, 24 May 2013 . | . UPDATED: . 18:24 EST, 24 May 2013 . Boris Johnson is being lined up as a key weapon for the Tories in the next general election campaign. David Cameron is prepared to turn to the London Mayor to win over voters who are currently put off by the party. Senior Tories say Mr Johnson has agreed to play a leading role as a ‘frontman’ in the campaign. He is expected to hold solo rallies across the country as well as join Mr Cameron on the trail. Scroll down for video . Philosophy: The trio discussed Aristotle while also plugging new film After Earth . Stars: Boris Johnson was left in the shade as Jaden Smith sang for a group of 10-14-year-olds at City Hall while father Will looked on . Rap: The London Mayor said he had written a rap about the Queen's Jubilee but wanted help from Smith to set it to music . Allies of the Prime Minister . recognise that they have to turn to the most popular figure in their . party if they are to have any chance of winning a majority. Mr Cameron has already hired . strategist Lynton Crosby, who masterminded Mr Johnson’s two mayoral . election victories, to help run the campaign in 2015. A senior Tory source said: ‘David . wants Boris to play a big role. He knows Boris is a real asset – he’s . hugely popular with Conservative voters and a real crowd-pleaser. Boris . is a one-off and he’ll be brilliant at rallying support. ‘And Boris is very keen to do what he . can to help. Everyone is going to have to play their part if we want to . win. Boris is up for the challenge.’ Trio: The unusual line-up attended a celebration event for 10-14-year-olds who had taken part in the Mayor's Leadership Clubs . Actor Will Smith and his son Jaden at City Hall with Boris Johnson,watch a presentation by young Londoners involved in the Mayor's Leadership Clubs . MC Johnson: The London Mayor enjoyed sharing the stage with rapper Will Smith . Workshop: Boris, Will and Jaden took part in some of the activities, including giving advice on staying out of trouble and forming a 'human knot' A senior Labour figure has admitted that the country’s benefits bill is ‘unsustainable’. Liam Byrne, the party’s work and pensions spokesman, said: ‘Welfare spending went up during the crash. That is supposed to happen. The problem is that it has not come back down and has carried on rising by 2 per cent a year. That is not sustainable.’ He suggested that Labour voters want to see the party get tougher on welfare, adding: ‘At the moment they don’t find the system is giving help to the right people and that frustrates them. We have to listen to that.’ But a Conservative spokesman said: ‘It is frankly a joke that Liam Byrne is saying Labour will get tough on welfare – this from the party that hiked welfare spending by 60 per cent while they were in government.’ Mr Johnson has proved he can win in the capital where Labour still maintains an electoral stranglehold. He is also popular with voters in the . North and blue collar communities who Mr Cameron has failed to convince . that the party is on their side. Recent polls have put the Tories as low as 24 per cent in the polls, just two points ahead of UKIP. Insiders also expect Mr Johnson to energise the party’s  grassroots base alienated by Mr Cameron’s support for gay marriage. While the London Mayor himself also . backs gay marriage, he is seen as a ‘feel-good figure’ by the party who . will inspire a mass turnout from the shires where Mr Cameron has . triggered defections to UKIP. That common touch was on display . yesterday, when Mr Johnson met Hollywood actor and pop star Will Smith . and son Jaden at City Hall for the Mayor’s Leadership Clubs, which offer . extracurricular activities for 10- to 14-year-olds. Knot: In bizarre scenes one workshop involved the schoolchildren forming a 'human knot' with the London Mayor and Hollywood actor . Support: The Leadership Clubs help young people through the tough move from primary to secondary school . Revealing to Mr Smith that he had . written his own rap song he said: ‘My first rap, I haven’t really set it . to music yet. Perhaps with your help. It was about the Queen’s . Jubilee.’ Mr Smith joked in reply: ‘That was big in the hip-hop . community.’ While both sides claim relations . between Mr Cameron and Mr Johnson are good, the latter has recently made . it clear that he does covet the Tory leadership and No 10 officials . often struggle to hide their irritation when he speaks out against . government policy. Despite this, the Prime Minister’s . senior advisers have convinced him he should call ‘all hands to the . pump’ if he wants to keep Ed Miliband out of Downing Street.
Hollywood stars at City Hall to advise youngsters on staying out of trouble .
Boris Johnson reveals he wrote a rap for the Queen's Silver Jubilee .
Rap star Will Smith jokes jubilee was 'big in the hip hop community'
Jaden Smith names Shakespeare and Kanye West as his influences .
By . Matt Chorley, Mailonline Political Editor . PUBLISHED: . 09:40 EST, 24 May 2013 . | . UPDATED: . 18:24 EST, 24 May 2013 . Boris Johnson is being lined up as a key weapon for the Tories in the next general election campaign. David Cameron is prepared to turn to the London Mayor to win over voters who are currently put off by the party. Senior Tories say Mr Johnson has agreed to play a leading role as a ‘frontman’ in the campaign. He is expected to hold solo rallies across the country as well as join Mr Cameron on the trail. Scroll down for video . Philosophy: The trio discussed Aristotle while also plugging new film After Earth . Stars: Boris Johnson was left in the shade as Jaden Smith sang for a group of 10-14-year-olds at City Hall while father Will looked on . Rap: The London Mayor said he had written a rap about the Queen's Jubilee but wanted help from Smith to set it to music . Allies of the Prime Minister . recognise that they have to turn to the most popular figure in their . party if they are to have any chance of winning a majority. Mr Cameron has already hired . strategist Lynton Crosby, who masterminded Mr Johnson’s two mayoral . election victories, to help run the campaign in 2015. A senior Tory source said: ‘David . wants Boris to play a big role. He knows Boris is a real asset – he’s . hugely popular with Conservative voters and a real crowd-pleaser. Boris . is a one-off and he’ll be brilliant at rallying support. ‘And Boris is very keen to do what he . can to help. Everyone is going to have to play their part if we want to . win. Boris is up for the challenge.’ Trio: The unusual line-up attended a celebration event for 10-14-year-olds who had taken part in the Mayor's Leadership Clubs . Actor Will Smith and his son Jaden at City Hall with Boris Johnson,watch a presentation by young Londoners involved in the Mayor's Leadership Clubs . MC Johnson: The London Mayor enjoyed sharing the stage with rapper Will Smith . Workshop: Boris, Will and Jaden took part in some of the activities, including giving advice on staying out of trouble and forming a 'human knot' A senior Labour figure has admitted that the country’s benefits bill is ‘unsustainable’. Liam Byrne, the party’s work and pensions spokesman, said: ‘Welfare spending went up during the crash. That is supposed to happen. The problem is that it has not come back down and has carried on rising by 2 per cent a year. That is not sustainable.’ He suggested that Labour voters want to see the party get tougher on welfare, adding: ‘At the moment they don’t find the system is giving help to the right people and that frustrates them. We have to listen to that.’ But a Conservative spokesman said: ‘It is frankly a joke that Liam Byrne is saying Labour will get tough on welfare – this from the party that hiked welfare spending by 60 per cent while they were in government.’ Mr Johnson has proved he can win in the capital where Labour still maintains an electoral stranglehold. He is also popular with voters in the . North and blue collar communities who Mr Cameron has failed to convince . that the party is on their side. Recent polls have put the Tories as low as 24 per cent in the polls, just two points ahead of UKIP. Insiders also expect Mr Johnson to energise the party’s  grassroots base alienated by Mr Cameron’s support for gay marriage. While the London Mayor himself also . backs gay marriage, he is seen as a ‘feel-good figure’ by the party who . will inspire a mass turnout from the shires where Mr Cameron has . triggered defections to UKIP. That common touch was on display . yesterday, when Mr Johnson met Hollywood actor and pop star Will Smith . and son Jaden at City Hall for the Mayor’s Leadership Clubs, which offer . extracurricular activities for 10- to 14-year-olds. Knot: In bizarre scenes one workshop involved the schoolchildren forming a 'human knot' with the London Mayor and Hollywood actor . Support: The Leadership Clubs help young people through the tough move from primary to secondary school . Revealing to Mr Smith that he had . written his own rap song he said: ‘My first rap, I haven’t really set it . to music yet. Perhaps with your help. It was about the Queen’s . Jubilee.’ Mr Smith joked in reply: ‘That was big in the hip-hop . community.’ While both sides claim relations . between Mr Cameron and Mr Johnson are good, the latter has recently made . it clear that he does covet the Tory leadership and No 10 officials . often struggle to hide their irritation when he speaks out against . government policy. Despite this, the Prime Minister’s . senior advisers have convinced him he should call ‘all hands to the . pump’ if he wants to keep Ed Miliband out of Downing Street.
written a rap about the Queen's Jubilee but and his son Jaden at City Hall with Boris activities, including giving advice on staying out of trouble and forming a 'human knot' A Hollywood actor and pop star Will Smith . and son Jaden at City Hall for the Mayor’s Leadership ‘That was big in the hip-hop . community.’ While