Quantum computers are now a fact. In their fully realised form, they threaten the informational advantages enjoyed by governments as well as industries, not least by breaking all existing data encryption techniques. If the engineering obstacles to high performing quantum computers can be overcome, a new range of geopolitical and even existential threats will emerge, but so will solutions to problems previously thought insoluble. The commercial opportunities are legion. In financial services quantum computing threatens the informational advantage of the arbitrageur but is already transforming portfolio optimisation. Derivative pricing and credit scoring are next.