Thanks Chris, I asked for a refund and the seller agreed, I then removed the loco body and tried the loco on the programming track connected to an analogue controller , I could then see the jerky action close up, I stripped the motor assembly and removed the gear set , I could not see any damage , I reassembled and tried it again , this time I applied a bit of pressure expecting the wheels to continue to rotate , they did not .I could then see that the motor was rotating , the large gear was rotating but the small gear ( on the same shaft), was not rotating , when I released the loco it ran as before. I stripped the motor etc down again and inspected closley the first gear set, , I found that the small gear was slipping on the shaft when only very slight pressure was applied.. I identified the correct gear set from the hornby website (X8849/21) - 21 indicates the number of teeth on the small gear., I then ordered a new gear set from Peters Spares for £3.79, fitted this and the loco ran smoothly in both directions in analogue mode, I then purchased a R8249 decoder from an e bay auction site, for £10.50, I fitted this and refitted the body, I programmed the loco on the test track to ID 009 and it now runs Ok, It pulls 4 illumninated Pullmans with ease from a crawl to full speed.- May I point out to others not to be aftaid of trying to do your own repairs, just be careful, do a drawing will help, and save all (tiny ) screws safely and note which screw goes where! - The most tricky operation in this case was refitting the body having fitted the decoder, this took a lot of patience and care. Many Thanks Chris, Best Regards to All , Barry.