Slipping Clutch v85tt

Just back from a 550 mile round trip in Ireland to Achill Island. When accelerating at about 80mph in 5th gear the revs would rise but speed would not ie clutch is slipping. I bought the bike with 8000 miles in it (now 13200) so I am thinking either the 1st owner severely abused the clutch or there is an oil leak past the seal from the engine to the clutch housing ( I do not think this is likely as there is no grabbiness) feels like the plates are down to the rivets. Has anybody else experienced this?

Have you got enough free play at the lever, should be 2mm, can’t see it being worn out with it’s low mileage, probably got oil contamination from the leaking crank seal.

Yes 2mm play, there is no smell and no grabbyness from clutch
Regards R