Promoted Championship side Watford have signed centre-back Mattie Pollock from Grimsby Town on a five-year contract for an initial fee of £250,000.
The 19-year-old spent six years with Leeds before joining the Mariners in 2018 and played 58 times for the club.
Pollock made his senior debut for League Two Grimsby aged 17 and his deal at Blundell Park had a year remaining.
Watford, managed by Xisco Munoz, have already signed England Under-18 forward Kwadwo Baah from Rochdale this summer.
