In the 1964/1965 season, Biddlecombe rode 114 winners, and followed that with 102 the next season. In 1968/1969, he rode 77 winners, which saw him tied with Bob Davies. One of his finest moments came in the 1967 Cheltenham Gold Cup, when he rode the 100-8 horse Woodland Venture to victory. In 1972, he finished second in the Grand National on Gay Trip. Between 1972 and 1974, he rode many times for Elizabeth, The Queen Mother, a well-known supporter of horse racing. In 1974, he appeared on the television programme This is Your Life, and finally gave up race riding having posted in excess of 900 winners.
Together with his wife he holds open days at his stables, with 5000 turning up to see their now legendary Cheltenham Gold Cup winner Best Mate, who was ridden to victory by Jim Culloty in 2002 and 2003. Another of their star horses, Edredon Bleu won the 2003 King George VI Chase at Kempton Park Racecourse.
In the early 1980s, Terry trained the actor John Hurt for his role in the 1983 film Champions, the biopic of jockey Bob Champion. Terry was followed into the racing game by his son, from his first marriage, Robert.