The Dubliner's arrest, at his home near York yesterday, brought the total number to be arrested to 26. The four other Flat jockeys involved are six-times champion Kieren Fallon, Fergal Lynch, Darren Williams and Paul Bradley. All were bailed later.
Winston, 25, noted for his strength in a finish, notched his best-ever tally last year in his seven seasons in the saddle, with 114 winners putting him in seventh place in the annual table. The victories included his first Pattern winner, on the Tim Easterby-trained Golden Nun in a Group 3 contest at Cork, his first Group 1 strike, on 40-1 shot Magical Romance for Brian Meehan in the Cheveley Park Stakes at Newmarket, and the John Smith's Cup at York on Arcalis for Howard Johnson.
During the inquiry, 130 police officers previously raided 19 addresses across Suffolk, North Yorkshire, South Yorkshire and Hertfordshire. More than 1,000 exhibits, including telephone records, are being analysed.