Pin sheared on towbar as the Dragonair was being pulled forwardabeam stand 63 The tug jacknifed and the aircraft burts one of it's nosewheel tyres. All this occurred abeam unfortunately blocked the only exit from Terminal 2 and the remote stands. All handled exceptionally well by all concerned. After discussions, the Dragonair decided to idle taxi on remaining tyre to clear the link. Resolved after about 20 mins. With the weather going pants later in the evening it was a busy duty for ATC. Being caught behind the Dragonair and then clobbered by the weather on the return I would like to say a big thanks to ATC for all their help. Nice one!