Another feature of the BTC 4-in-line was the autolube (probably optional) but the small cylindrical tank was located just under the platform in front of the axle,as I was only a young “wipper snapper” when these trailers were operated I never took a lot of notice but I’ve often wondered since how they worked,ie,how were they driven.The ones at Bradys always looked neglected,with the bits of pipe hanging off broken etc. as regular planned maintainence was never one of Bradys strong points ! Cheers Bewick.