"They say up here that it can't be found," said Harold Parkinson-Truman, a retired VAT inspector from Wakefield, packing up a hi-viz vest, some Kendal mint cake and a postcard of Tower Bridge to help when asking directions.
"But I've lived along the M1 all my life. I've seen it in its rush hours and when it's fogbound, and I'm going to devote my autumn years to finding the fabled source of it - way down at Junction 1 in that London."
Consoling his weeping wife and ferret, Harold continued: "They don't want me to go down south and start taking on their ways, like attending the opera at Glynebourne and supporting Chelsea. But I've been told tales of the wonderful exotic food they have in ChoZen Noodle at London Gateway services. The allure's too great to resist.
"They say that once a coachload of football supporters from Barnsley set off down the M1 to try and watch an FA Cup tie against Leyton Orient, but the authorities turned them back at the Watford Gap.
"My plan is to sneak into the Home Counties by nipping through the fields somewhere around Daventry. Then I'll pitch camp at Watford for the final leg down to Brent Cross.
"I hope the local tribesmen are friendly."
"We're not," a spokes-tribesman for Brent visitors' centre said gruffly, when told of Harold's expedition.
Asked if he had any tips for the intrepid explorer to north-west London, the tourist official answered simply: "Wear a stab proof vest."
