The operation was directed from HMS Varbel, located in Port Bannatyne on the Isle of Bute. Varbel (named after Commanders Varley and Bell, designers of the X-Craft prototype) was the on-shore headquarters for the 12th Submarine Flotilla (midget submarines). It had been a luxury 88-bedroom hotel (the Kyles Hydropathic Hotel) requisitioned by the Admiralty to serve as the flotilla’s headquarters.