How the job is done
Found it flat in Biggleswade? Leave it where it is.
Flat tyres in SG18 are often found after the car has stood for hours. Great Northern commuters back from King's Cross find a wheel down to the rim beside the Biggleswade platform car park, walkers on Biggleswade Common come back to one down, and a slow puncture from A1 debris empties overnight on a Stratton Park drive. Driving on it, even a few hundred metres, can destroy the sidewall and rule out a repair altogether.
Do not reinflate and drive; just call or WhatsApp with where the car is and a picture of the tyre. The fitter takes the wheel off beside the car and looks inside the casing. A central puncture in a Holme or Kings Reach tyre that was left parked, never run flat, can be repaired. If the sidewall has creased from standing deflated, or the hole is off to one side, the SG18 replacement goes on once you have agreed its cost.
On run-flat tyres? They behave differently once deflated, so check the handbook's limits and read our page on run-flat tyres; we fit replacement run-flat tyres at the car in Biggleswade as well.
Related help from the same Brent Cross team covers broken tyre replacement in Biggleswade and emergency tyre replacement in Biggleswade.