bigjohn said:he has since offered an amount which has been accepted that left him out of pocket,
How did it leave him (or should that be you) out of pocket
He received an item which was sent to an incorrect address by mistake - the next day "sold it at a car boot sale" - seems no attempt was made to find out where it came from, other than ringing Royal Mail who said he could keep it (which i find higly unlikely that they would say this with out checking into it).
At the least i would expect that they would check to make sure they delivered the item to the correct address and look into to it which would proberly take them at least a few days to investigate. (It was a special delivery item so they i doubt they would just say keep it, SD items get treated with much more investigation than one 5 min phone call).
Again - why did you/he not look into where the item may have came from.