This is why a siren sounded on Portsmouth Naval Base this morning

The wavering tone sounded at Portsmouth Naval Base at 9.30am and lasted for about a minute.

It was the first time the siren has been blasted this decade, with two more routine tests expected later this year.

In a tweet after the test, the naval base apologised for the loud sound and said: ‘Hope it wasn’t a rude awakening.’

The test is part of the nuclear accident response plan for the naval base and is in accordance with Portsmouth and Gosport councils’ nuclear safety plan.

Every year the siren is sounded three times, once in February, June and October.

A Royal Navy spokeswoman said: ‘The nuclear emergency siren at Portsmouth Naval Base was sounded for a routine test. By agreement with the local authorities, the siren is tested three times a year.’