Hello Robert.
The water table is only a few feet below the surface. About 6 years ago I had a lot of work done to increase the drainage as there were times when the garden flooded. Whilst I think a lot of top soil was added, the lawn soil is still very wet and appears to be clayish. Last winter the moss seemed to become evasive - I probably should have raked in the Autumn. I'm in the process of raking out, aereating and filling with a compost sand mixture and repairing with lawn seed. I hope this will help.
So yes, there is, if you pardon the pun, an underlying problem with the lawn.
Regards
Bluecar