builder mark lawson , 44 , was in the diamond tap public house in newbury , berkshire for his christmas party when he agreed that his co-worker simon myers could take some chips from his plate .
when mr myers started eating an onion ring , lawson was angered , shouted at his victim and drove the knife into his thigh .
simon blackford , for the prosecution , told reading crown court that lawson ` reacted in a very loud way ' to what was happening .