Last of the Summer Wine

From Here to Paternity (21x7)

:

Compo recieves a personal letter after all these years. when Clegg and Truly open it they discover Compo's biggest secret: he has a son. The son, Tom, wrote to Compo, because after all the years of separation he hoped he and his father could get together. When Tom arrives in town it's up for the pair of them to give him the shocking news.