Peter Tyndall WalwynMBE (born 1 July 1933) is a retired British racehorse trainer. He was based at stables at in the Lambourn, Berkshire, area and enjoyed his period of greatest success in the mid-1970s when he was British flat racing Champion Trainer twice.
Walwyn comes from a racing family - he is the cousin of trainer Fulke Walwyn. He was educated at Charterhouse School and his first job in racing was as assistant to trainer Geoffrey Brooke. He then held the licence for Helen Johnson Houghton, twin sister to Fulke Walwyn (women were not recognised as licenced trainers by the Jockey Club in those days). In October 1960 he took out a licence to train and in 1965 he moved to the stables at Seven Barrows where he spent the majority of his career. Towards the end of his career he moved to Windsor House stables in Lambourn. His principal stable jockeys were Duncan Keith, Pat Eddery and Joe Mercer.
He was one of the leading trainers in Britain during the 1970s, winning the Champion Trainer title in both 1974 and 1975. The most notable horse he trained was Grundy, winner of the Epsom Derby, Irish Derby and King George VI and Queen Elizabeth Stakes in 1975.
He retired as a trainer in 1999 but remains involved in horse racing organisations, and as at February 2011 is Chairman of the Lambourn Trainers Association. He was elected to honorary membership of the Jockey Club on his retirement.
Walwyn was appointed Member of the Order of the British Empire (MBE) in the 2012 New Year Honours for services to horseracing.