[T2] clutch slipping

[Robert Mann]

Maungakaramea, Northland

     Early in a few-d northern tour my clutch quietly began slipping  -
had to change down into 2nd gear because revs would build in 3rd.
     I've never had to do anything to my clutch.
     The pedal has large 'freeboard' at the top  -  unchanged.
     The cable pulls a lever back at the L side of the transmission.  The
mooring of the cable onto that lever is by a wingnut {!} which we have
slightly adjusted so as to slacken the cable slightly (4 bumps).
     Before we even test this slightly changed rig, I thought I'd consult
the gurus.
I figure
            EITHER oil has leaked into the clutch
            OR it is irreversibly worn

'Any ideas please?

Robt Mann
'73 1600dp Devon