A Thames riverboat has crashed into a pier that is overlooked by some of the capital's top landmarks, police said.
Four people were taken to hospital for treatment to minor injuries after the clipper vessel struck Tower Millennium Pier.
More than 50 passengers were on board the catamaran, which ferries passengers up and down the Thames, when the collision happened.
Scotland Yard said: "We received a report of a Thames Clippers vessel in collision with the Thames Millennium Pier."
A spokesman said the ambulance service also attended, and "a small number of other passengers were treated at the scene and did not require hospital treatment".
He added the Metropolitan Police Marine Policing Unit has begun an investigation in conjunction with the Port of London Authority (PLA) and the Marine Accident Investigation Branch (MAIB).
Martin Garside, from the PLA, said: "One of the clipper boats, the Moon Clipper, has made contact with Tower Pier.
"There were no other vessels involved and the vessel did not sink."
The pier is on the north side of the Thames between London Bridge and Tower Bridge. It is below the Tower of London and opposite HMS Belfast.