At 5 long tons (5.1 t), it could only be carried by the Avro Lancaster heavy bomber. It proved to be effective against massive and hardened structures against which conventional bombing had proved ineffective.
Wallis presented his ideas for a 10-ton bomb in his 1941 paper A Note on a Method of Attacking the Axis Powers, which showed that a very large bomb exploding deep underground next to a target would transmit the shock into the foundations of the target, particularly since shock waves are transmitted through the ground more strongly than through air.
Wallis designed the "Victory Bomber" of 50 tons, which would fly at 320 mph (510 km/h) at 45,000 ft (14,000 m) to carry the heavy bomb over 4,000 mi (6,400 km), but the Air Ministry opposed a single-bomb aircraft, and the idea was not pursued after 1942.
The design and production of Tallboy was done without a contract on the initiative of the Ministry, following Wallis' 1942 paper Spherical Bomb—Surface Torpedo and the design of the "bouncing bomb" for the Dam Busters of Operation Chastise. As such, the RAF used bombs that they had not bought and which were still the property of Vickers the manufacturer. This situation was normalised once their capabilities were recognised.
Accomplishments of the Tallboy included the 24 June 1944 Operation Crossbow attack on La Coupole—along with Grand Slams—which undermined the foundations of the V-2 assembly bunker; and a Tallboy attack on the Saumur tunnel on 8–9 June 1944, when bombs passed straight through the hill and exploded inside the tunnel 60 ft (18 m) below the surface.