 He progressed to undertake a scholarship, but did not win a call into a first team squad before his release at the end of the 1998–99 season.On 8 July 1999, Theobald signed a three-year contract with newly-promoted Second Division club Brentford on a free transfer.He was utilised as cover for injuries and had a run in the team as a stand-in right back for the injured Danny Boxall during the 1999–00 season and in central defence for Scott Marshall during 2000–01.