By Daily Mail Reporter

Last updated at 2:12 AM on 26th October 2011


David Cameron was showing the strain yesterday after the biggest-ever Tory rebellion on Europe when more than half of his backbenchers defied him in a vote on a referendum on EU membership.

The 45-year-old Prime Minister was seen leaving Downing Street with clearly visible streaks of grey in his hair in the aftermath of the debate and poll last night, which saw a catastrophic 81 Tory MPs defy a three-line whip, the strongest possible party instruction on how to vote.

Thanks to Labour and Lib Dem MPs, the vote was defeated by 483 to 111, a majority of 372.

Today Mr Cameron admitted it had 'always been a difficult issue' for the Tories, but he insisted the 'important thing is to do the right thing for the country'.

Taking its toll: The strain of leading the Coalition Government appeared to be telling when Prime Minister David Cameron left Downing Street today with clearly visible grey streaks in his hair after suffering a huge Commons rebellion on Europe last night

Speaking during a visit to Lockheed Martin UK in Bedford, Mr Cameron defended his decision to impose a three-line whip on his MPs over the vote, saying 'in politics you have to confront the big issues rather than try and sweep them under the carpet.

'It wouldn't be right for the country now to have a great big vote on an in/out referendum and the rest of it,' he added.

'What I would say from last night is there's no bad blood, there's no rancour, no bitterness.'

What Cameron can expect: Tony Blair in 1997, left, with a much darker style, compared with 2007, right, where the pressure of the top job took its toll on his colouring

The Prime Minister can be comforted by the fact that he is not the first leader to show signs of the strain of the job through his hair colouring.

Mr Cameron's formerly black thatch has developed a distinctly grey tone since he took office, but the same things happened to Tony Blair and Gordon Brown during their time in power.

Before he was elected Mr Cameron, the youngest premier in almost 200 years, revealed he was concerned about going grey.

Going grey gracefully: Barack Obama's changing colour during his presidency has raised speculation that he uses dye in his hair

'I've had a few grey hairs and I expect I'll get a few more, whatever happens. This is a relentless process,' he said.

U.S. President Barack Obama has had to deny using hair colouring, as he also appears to have greyed since taking power.

Obama was even seen to be turning grey on the campaign trail to become president, with his hair colour changing as the pressure intensified in summer 2008.