Boris Johnson is on course to secure a second term as Mayor London, according to a poll published on Thursday.

A survey conduced by YouGov for the Evening Standard shows Johnson defeating Ken Livingstone by 53-47% - the same margin by which he won four years ago.

Writing on The Huffington Post UK on Thursday, as voters go to the polls, Peter Kellner, the president of YouGov, said the main reason for Johnson's expected victory was the "Boris Labour" vote.

"We looked at people who told us they were certain to vote today, and would vote Labour if today’s contest were a general election," he explained.

"One in 10 told us they will vote for Boris. If they voted for Ken, he'd win by 52-48%. Another one-in-ten Labour supporters will withhold their mayoral vote from both men (though most will vote Labour in the Assembly election). If they all backed Ken, he'd win by 54-46%."

Kellner also predicted that Boris will be helped by Tory supporters who are disenchanted with David Cameron and would vote Ukip in a general election. They prefer Boris to Ken by ten-to-one.