Nicholls took out his trainer's licence in 1991, having served a two-year apprenticeship as assistant trainer to Barons which saw him assist in Seagram's winning Grand National attempt. In response to an advert placed in the Sporting Life, Nicholls began his training operation at Manor Farm, Ditcheat, in stables rented from local dairy farmer Paul Barber. Starting with just eight horses, his first winner soon followed, the appropriately named Olveston, owned by Nicholls' father and named after the South Gloucestershire village in which he was raised. A steady climb up the training ladder followed, with Nicholls' first grade one success coming with See More Indians in the Feltham Novices' Chase at Kempton in 1993.