Royal Navy deploys its smallest ship to Portsmouth to help keep HMS Queen Elizabeth and HMS Prince of Wales safe

HMS Magpie – also the UK’s newest commissioned warship – will spend more than three months surveying the harbour and its approaches to make sure they remain safe for use by the Royal Navy’s two new gigantic aircraft carriers, both based in Portsmouth.

More than three and a half million cubic metres of clay, sand and gravel was excavated as part of £100m improvements to the harbour’s infrastructure to accommodate the 65,000-tonne warships – each one with a draught of 11 metres (36ft).

Now harbour and naval chiefs want to ensure that the sands and mud on the seabed hasn’t shifted – posing a danger chiefly to the carriers but also other harbour users.

It comes ahead of the arrival of HMS Prince of Wales, later this year.

‘One of the biggest challenges is how busy the harbour is,’ said Magpie’s captain, Lieutenant Commander Will Alexander. ‘There are around 230,000 movements every year, and it’s especially busy in the summer with pleasure craft.’

It’s only the second mission carried out by Plymouth-based Magpie, which joined the Royal Navy last year.

After painstakingly surveying the waters around Barrow – where the nation’s nuclear submarines are built – at the end of last year, Magpie is giving Portsmouth and Solent the same thorough treatment.

Her built-in and towed sonar systems will scan every inch of the working part of the harbour to provide 3D imagery and an understanding of the seabed like never before.

Once work inside the harbour and main approaches is finished, Magpie will shift focus to the wreck site of the Mary Rose to see if there’s anything of significance left on the seabed from Henry VIII’s flagship.

And then she’ll investigate the wreck of a French galley, lost around the same time as the famous British flagship off the northeast coast of the Isle of Wight.

This is the first visit to Portsmouth by Magpie, which replaces long-standing survey motor launch HMS Gleaner, retired last year after 35 years’ service.