The Prime Minister was delighted to joke today that although he was not born in Darlington he could say that he was 'bread' in the town – his great-great-great-great-grandparents, Hannah and Walter Johnson, were bakers.

National newspapers have begun picking up on the connection, which was revealed more than a year ago in The Northern Echo with the help of the then vicar of St Cuthbert’s Church, the Reverend Matthew Firth.

Mr Johnson’s great-great-great-grandfather, Thomas, was baptised in St Cuthbert's on December 19, 1813. He may even have been in the town in 1825 when the Stockton & Darlington Railway opened.

On September 2, 1837, Thomas married Mary Raper at Masham – which, as Rishi Sunak pointed out today, is just a mile outside his Richmond constituency. Thomas and Mary ran a draper’s shop in Masham, then Ripon and East Witton until Thomas died in 1858, aged 42.

Mary, and their two-year-old daughter Margaret, moved back to Darlington, presumably to be near their Johnson family.

Margaret’s daughter, Winnifred, married a Turkish journalist, Osman Kemal, but when she died in 1909 in childbirth, Margaret brought up their two children. During the First World War, she felt that having a Turkish surname was not helpful and so she chose her Darlingtonian maiden name, Johnson, for them.

One of those children was the grandfather of Prime Minister Boris Johnson.

Because of this connection, Mr Johnson has taken an interest in the fate of Locomotion No 1.

Mr Johnson said: “Peter [Gibson, Darlington MP] and Heather [Scott, Darlington council leader] have been working hard and we’re hopeful that we will be able to say something positive about the Locomotion. I think we are on the verge of progress.”