So, not knowing much about engines, I called up Ken Paris (who is a local mechanic and TR4 owner) and got him round to check the engine out. I stripped off the sump and head and we discovered that the bearing on number 3 conrod was razor sharp. Ken picked up each part I'd taken off and proceeded to say 'buggered', 'knackered', 'totally mullered' etc. This went on for quite some time and we both agreed a new short engine was needed! I asked Ken to do it for me but he pretty much said he wouldn't and I should do it myself. He kindly offered to lend me an engine crane to use though, which was very generous.
After being messed about and ripped off by Quiller Triumph (somewhere I will never shop again), I got the engine rebuilt and all torqued up. I decided to uprate the camshaft before I put it back in the car and looked at various cams from Piper and Kent. In the end though I went for the Spitfire Mk3 profile (from Canley Classics) which is just the thing for road use.
With the help of my mom (who has a bad back) and grandad (who had just had a triple heart bypass!) we eventually got the engine on the gearbox shaft and bolted up to the bellhousing. It started up second time with no dubious rattles. Champagne was had all round!