The Royal Navy has tested an unmanned speedboat near Tower Bridge in advance of a naval drone exercise off the UK coast this autumn. To the delight of tourists, Tower Bridge swung open to let through the sleek, low-slung craft, known as Mast (Maritime Autonomy Surface Testbed). Accompanied by the patrol craft HMS Archer, the 32ft-long Mast spent an hour on Monday weaving between pleasure boats and goods barges at a moderate pace, heading up the river towards Westminster before returning downriver. Although it is capable of navigating and avoiding collisions autonomously and can be operated via remote control, Mast had a coxswain on board to take control if needed because of Port of London bylaws, which also limited the speeds at which it could travel. Mast is being developed with research funding from the Ministry of Defence's science and technology laboratory, to explore how well such vessels function autonomously.