I've always liked Richard Sinclair's singing and bass playing and his signature tone has always been a Jazz Bass with emphasis on the bridge pickup. However on Hatfild And The North's second album "The Rotters' Club" his tone is different (but equally tasty) and it bothered me for years (I'm serious!). The bass sounds a bit like a P-bass or a Ric with bridge pickup on.
Well, it seems he had removed the Jazz pickups and had installed a Gibson EB bridge pickup between the original locations. I asked Neil Murray on Facebook if he could give me any info since Neil and Richard played some gigs together when Neil was in Gilgamesh in 1973 and he said that Richard liked the sound of his P-bass that had an EB-3 bridge PU installed (near the bridge).
He later reinstalled the Jazz pickups and went back to his old sound (during his stint with Camel also removed the frets).