The belief that a successful politician requires a cast-iron stomach was given credence by London mayoral candidate Boris Johnson as he battled to win Jewish votes in North-West London on Sunday.

Appearing just a touch queasy, the Tory challenger to Ken Livingstone told an adoring crowd that he had “never eaten so much salt beef and so many bagels in my life”.

It seemed that food, rather than politics, was the main item on the menu as Mr Johnson’s bagel-laden battlebus progressed from kosher restaurant to kosher restaurant in the Jewish heartland of North-West London.

At Bloom’s in Edgware, his earnest minders, some adorned in “Back Boris” T-shirts, fought a losing battle to win him some privacy as he tucked into salt-beef sandwiches and latkes in front of TV cameras which recorded every munch and swallow.

“Give him a double portion. He deserves it,” laughed one fellow diner. But Mr Johnson, ever the politician, left Bloom’s, clambered heavily on to a chair and burnt some calories attacking the mayor’s “sleazy” administration.

This struck a chord with some in his audience, one of whom loudly declared: “Livingstone is a monster. My cleaning lady could do a better job.”

Others, however, seemed a little bemused. “Isn’t that Boris?” asked a kippah-wearer. “Yes, isn’t he wonderful?” one of the candidate’s retinue burbled. But he wasn’t persuaded. “Politicians, they are all the same,” he said.

After autographs, it was on to Hendon, where for the first time there were signs that Boris was not necessarily the flavour of the month.

“Down with Boris,” chanted a group of drinkers outside a Brent Street pub, as the candidate’s procession led him inexorably to yet another kosher establishment, Orli’s coffee shop.

“Ooh, isn’t he a nice boy,” gushed one woman obviously dazzled by the candidate’s blond mop. Owner Orli Avital had a more prosaic reason for supporting the Tory. “I’ll vote for him because he likes us,” she growled.

Further up Brent Street was yet another challenge to Mr Johnson’s digestion as he entered the gigantic Mr Baker’s bakery and coffee shop. A bagel and a slurp of coffee later, and it was off to Golders Green.

There he met the owner of kosher Chinese restaurant Met Su Yan, who offered him a free meal if he beat Mr Livingstone. But a free meal seemed to be the last thing on the candidate’s mind.