Caption- "HAREFIELD, MIDDLESEX, ENGLAND, 1914-18. AN AMBULANCE AND FORD CAR WITH THEIR DRIVERS USED TO TRANSPORT PATIENTS"
Blackadder fans will surely recognise Captain Darling in the roadster.
I guess this must have been fairly early in WWI - they look cheerful and the cars are clean and shiny. Also, the ambulance looks like a DIY adaptation of a (non- Ford) Touring car
and LL registrations were only issued between March and July 1914. That Ford looks newish