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.

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Portsmouth Naval Base posted on social media: “Please note there will be a full test of the Naval Base’s nuclear emergency alerting siren at 9.30am today which may be able to be heard outside of the base.

“This is a statutory requirement and is being conducted in agreement with Portsmouth City Council and Gosport Borough Council. The two-tone siren will be sounded for one minute for the test - so please don’t be alarmed if you hear it.”

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.