I think I have the very thing for them, and note it was produced by private enterprise...
The actual design and production of Tallboy was done without a contract on the initiative of a single official within the Ministry. As such the RAF were using bombs they had not bought and which were actually still the property of the manufacturers; Vickers. This situation was regularized once their capabilities were recognised.
When dropped from 20,000 ft (6,100 m) it made a crater 80 feet deep (24 m) and 100 feet (30 m) across and could go through 16 feet (5 m) of concrete. It was capable of displacing a million cubic feet (29,000 m³) of earth and made a crater which it would have taken 5,000 tons of earth to fill. It was ballistically perfect and in consequence had a very high terminal velocity, variously estimated at 3,600 and 3,700 feet (1,100 m) per second (1,100–1,130 m/s or about 2,500 mph / 4,000 km/h), which was, of course, a good deal faster than sound so that the noise of its fall would be heard after that of the explosion.