‘Marauding terrorists’ on the loose and shooting at the public will form the basis of a ‘large-scale’ police training exercise across the area today and tomorrow.

A large scale operation is taking places across the Thames Valley as part of an exercise to test major incident contingency plans and the response of the emergency services in the event of a major incident within the region.

Joining South East Counter Terrorism Unit, the military, Thames Valley Police and Hampshire Constabulary Today officers will involve a multi-site marauding terrorist firearms attack scenario at Carmel College near Wallingford, Oxfordshire.

Whilst tomorrow, the operation will involve a covert surveillance operation in public spaces in Thames Valley and Hampshire followed by a covert hostage rescue at two building venues in Basingstoke, Hampshire.

Deputy Chief Constable of Thames Valley Police, John Campbell said: "This is one of a number of routine and pre-planned exercises organised across the country to test the response of the emergency services.

"We carry out these exercises to test contingency plans and the co-ordination of the response to a major incident on a regular basis. This training is not being carried out in response to any specific threat.

"Every effort has been made to keep disruption to a minimum to nearby residents and communities, however some of the activity might be visible and heard by the public but this will be limited, risk assessed and appropriately managed.

"The exercise will not affect our resources or ability to keep our communities safe in the Thames Valley and in Hampshire, it will be business as usual for our thousands of officers and staff who are not involved in this training."

Last month, Wycombe's top police chief warned people to remain vigilant against the threat of terrorism - 10 years on from a series of terror raids which rocked the town. 

Mr Campbell said: "Since August 2014, the threat to the UK form international terrorism has been graded as 'severe', meaning an attack is highly likely.

"As such I want to take this opportunity to remind the public to remain vigilant.

"We depend on information from the public. They can be our eyes and our ears and help keep themselves and communities safe by reporting suspicious activity."

Police urge people to report any suspicious activities to the confidential Anti-Terrorist Hotline on 0800 789 321.

Mr Campbell added: "If you know anyone you might be potentially vulnerable to being drawn into terrorism or violent extremism you can contact your local police on 101 or visit www.preventtragedies.co.uk for further advice and guidance.

"If in the unlikely event you get caught up in a weapons or firearms attack, remember to run, then hide, then tell the police."