Either that or he's tanning gradually bit by bit, so friends and relatives who haven't seen him for a while, don't get a complete shock, if he appears to have suddenly gone brown.
Around here we call that the "farmer's tan". My grandfather had one, most especially on his left arm...caused from driving his farm truck (1957 Chevrolet pickup truck) with the driver's side window down and hanging his arm on the side. good memories there... - I guess in England you would have one on your right arm? I forgot you guys don't know which side of the car to put the steering wheel.