Gillingham manager Andy Hessenthaler is starting his search for a replacement for assistant Ian Hendon.[LNB] Hendon has left the club to take up the role of development team coach at West Ham[LNB]Hendon, 39, joined Hessenthaler's coaching team last summer following a brief spell as manager of non-league Dover but has spent just one season at Priestfield.[LNB]The Gills boss would prefer to bring in a new coach rather than a number two and hopes to be able to make an appointment next week.[LNB]He told the club's official website: "There is a void there and I am certainly looking at bringing somebody in so I'll be sitting down with the chairman to see which way we go with that."[LNB]Hessenthaler added: "Ian has gone now. The situation was that (Hammers first-team coach) Wally Downes, who worked with us last year, made a call to me and asked if they could offer him the job.[LNB]"I didn't want to lose Ian but, as a friend, I had to ask him the question. He wanted to speak to them and they offered him the job, so I couldn't stand in his way. I think the chairman is looking into the situation at the moment but Ian has gone."[LNB]Meanwhile, Gills are anxiously awaiting news on new signing Adam Birchall after he left the field during Tuesday night's 3-0 friendly victory over Welling on a stretcher nursing a knee injury.