Picture posting is enabled for all :)
Definately take it back, doesn't matter if you cooked it. Do you have the receipt or the wrapper for batch code? I would also make a note of the batch number and write to head office claiming a spoilt celebration. Tesco are the worst supermarket ever. Ocado are price checked against Waitrose and have superb customer service!!
Whenever I have lamb it smells strange............mind you,it is kebeb shaped and covered in garlic mayo and mint yoghurt ;) ;D ;D