West Ham were forced to bin plans to wear a specially-designed kit in the FA Cup after an embarrassing administrative mix-up. The Hammers unveiled a commemorative 'Thames Ironworks' navy-blue outfit in August and told fans it would be 'worn during our FA Cup campaign'. But there was no sign of it as they crashed out in the third round at the hands of Manchester City on Friday night, with their regular home kit worn instead. And Sportsmail can reveal club chiefs believed they had the sign-off from the FA to wear the special shirts at the start of the season — only to later be told it contravened the governing body's regulations. An source close to the FA said the problem stemmed from a commercial issue with the shirt. There are strict guidelines over the size and prominence of sponsors' logos on teams' shirts. The kit, which featured a Union Jack detail harking back to West Ham's forerunners Thames Ironworks FC and a blacked-out glossy logo of sponsor Betway, is now set to be left unworn apart from when it was used in a pre-season friendly against Juventus back in August.