 At cricket, Barnwell was a middle-order right-handed batsman and an occasional right-arm medium-pace bowler.After captaining the first XI at Repton in 1963, he played four times for Cambridge University in 1965 and 1966 without gaining a regular place, and six times for Somerset in 1967 and 1968.His only seasons of regular first-class cricket were for Eastern Province in South Africa when he opened the innings for a side that included the Pollock brothers and Tony Greig.