Twenty-week-old Grayson easily could have become one of the tens of thousands of British babies left unvaccinated against polio.

His mother, Lily, agrees with the principle of immunisation. But overwhelmed by the early weeks of motherhood, and suffering from post-partum depression after a traumatic birth, she was daunted by the prospect of a long journey to a doctor’s surgery. “I’ve been through the trenches, awake all night. You don’t want to leave the house, or go to a different town.”

Weeks ticked by, and eventually Grayson missed the polio and diptheria jabs he was supposed to get at eight weeks old. By that point he was officially classed by the NHS as “overdue” for vaccination; effectively, he was on his GP’s naughty list.

Then Lily realised there was a clinic practically on her doorstep – at a location she hadn’t expected.

That clinic – in Keighley, west Yorkshire – runs from a vacant retail unit at the Airedale shopping centre, a 1960s-era precinct that locals say has fallen on hard times in recent years, with plenty of empty, boarded-up units. The staff who created the clinic thought: why not use one of those vacant units to administer vaccines?

“This was an empty shop; there was nothing here, the windows were all blacked out,” Flora Jennings, a local charity coordinator, tells me over the sound of a baby’s laughter, on the morning I visit the clinic.