Hundreds of armed police have taken part in a realistic anti-terrorism training exercise on the River Thames. The RNLI, London Fire Brigade, Port of London Authority, London Coastguard and London Ambulance Service also took part in the drill, code-named "Exercise Anchor," in which six "terrorists" – played by police officers – hijacked a cruise boat taking passengers hostage.

In a hail of "gunfire", black-clad police approached the City Cruises vessel in the Thames in the Docklands area on fast-moving dinghies carrying sub-machine guns, and at one point a "body" was thrown overboard.

The exercise was the first of its kind and was designed to assess the effectiveness of the response of security services in the event of a real incident.

The Metropolitan Police were at pains to stress the exercise, which began at 11 am on Sunday (19 March), wasn't a real terror attack.

In a statement, Commander BJ Harrington said: "This was the first time that we've tested together the response of the various agencies that operate on the River Thames to a potential terror attack.

"I'd like to stress that this scenario wasn't based on any specific intelligence, but it's important to remember that the threat level for international terrorism in the UK remains at 'severe'. This kind of exercise demonstrates that should a terrible event ever happen for real, London is ready to respond in the most efficient and effective way possible.

"I'd like to thank the public and those using the river for their cooperation and understanding during this exercise. It has undoubtedly helped us to strengthen the working relationship between the other marine agencies that would be involved in dealing with this type of incident on the Thames.

"With the threat level as it is, we cannot afford to be complacent and the public should always be vigilant and ready to act if the worst were to happen. Exercises such as this one show that London is prepared and should reassure anyone who lives, works or visits London that there is an amazing team of highly dedicated, professional and skilled men and women ready to keep them safe from this kind of threat."

The exercise comes one day after an alleged radicalised Muslim was shot dead at Paris Orly airport after he grabbed a soldier's weapon. Ziyed Ben Belgacem, 39, reportedly shouted he was there "to die for Allah" during his attempted attack.

Thirteen potential terror attacks have been disrupted in the UK in the past four years. The terrorism threat level in the UK remains at severe, meaning that an attack is "highly likely", though no specific threat has been identified.

London terror drill 2017
Hundreds of armed police took part in a realistic anti-terrorism exercise on the River Thames Metropolitan Police