Sam Thomas has been appointed second jockey to Ruby Walsh at Paul Nicholls' Ditcheat yard.
The position came available due to Christian Williams' long-term injury after a fall at Worcester last month.
Thomas' switch to Nicholls' yard means he has now ended his tenure as Venetia Williams' stable jockey.
Thomas said: 'The opportunity to join Paul Nicholls' team as second jockey arose and it was an offer too good to refuse.
'At this stage of my career, I couldn't afford to let something like this slip away and I'm very much looking forward to riding for Paul in the very near future.'
Nicholls told the Racing Post: 'Sam is a very good jockey who has been riding a lot of work with us this autumn.
'I'm delighted he has agreed to join us as second jockey.
'He will ride the majority of our horses when Ruby is unavailable.'
