With the respite in the rain the last few days (hasn't rained since
Thursday) all of our patio (18"x18" slabs) is dry.

Except a small patch on one slab. Which rather worringly looks to be over
the line of the drain pipe from the external drain by the side of the
house, to where it joins the inspection pit with the manhole cover about
2.5m away.

(I know it goes into this pit, as I remove the cover to empty my caravan
loo, so can see the pipe). The pipes a 1960s ceramic type.

Before I start lifting slabs, and excavating, is it possible that a
cracked or damaged pipe could cause an upward dampness like this ? Is
there any easy repair, or (assuming it is damaged) is the proper job to
replace the entire length of pipe ? Would folks say the hardest part of
the job is digging the old pipe free, or actually replacing the pipe ?

As always, TIA guys ...