The Royal Navy’s smallest ship has celebrated 20 years in service.

At just 16 metres in length, Gleaner does not even claim to be an HMS – instead she is HMSML, or Her Majesty’s Survey Motor Launch – but within her modest hull is a collection of equipment which makes her a very useful asset indeed.

Gleaner has been conducting routine re-surveys in the Sound and River Tamar at her home port, Plymouth. Those findings will help ensure the deep-water navigation channels used by ships and submarines when entering and leaving Devonport Naval Base are still accurate, and that there has been no significant movement of the sediment on the sea bed.

HMS Gleaner was built at Emsworth, in Hampshire, and was commissioned into the Fleet in December 1983. She has a ship’s company of just eight - two officers and six ratings - and was originally designed to conduct inshore surveys along the South Coast of England.

But for such a small ship she has ventured a great deal further, surveying coasts around Great Britain and visiting ports in mainland Europe.

She is also the only Royal Navy ship to visit Switzerland, having travelled up the Rhine to the land-locked country for a visit to Basle in 1988.

Her current Commanding Officer is Lt Cdr Matt Syrett, a specialist hydrographic surveyor and navigator, who is the 22nd officer to hold the position.

Lt Cdr Syrett said: “Gleaner is a fantastic survey vessel. We normally work in waters up to 100 metres in depth, and our sophisticated sonars collect more than 21 million soundings in a square mile, allowing us to produce an accurate three-dimensional picture of the sea bed.

“Over the past 20 years HMS Gleaner has worked in a variety of places, and has steamed nearly 100,000 miles.

“The work in Plymouth Sound brings the total number of surveys we conducted in 2003 to five.

“Despite Gleaner’s age she carries one of the most advanced survey systems in the world, and although her hull has dated she is certainly not tired. My ship’s company and I have greatly enjoyed the challenges associated with operating such a small vessel in remote areas, and hope that she continues to fly the White Ensign for many years to come.”

A dozen former Commanding Officers visited Gleaner to mark the 20th anniversary, among them the current Captain Hydrography and Meteorology, and Hydrographer of the Navy, Captain David Lye, who was HMS Gleaner’s first Commanding Officer between December 1983 and January 1985.

He said: “As the first Commanding Officer, I have very fond memories of Gleaner when I introduced her into service 20 years ago.

“Her versatility and continuing effectiveness have hugely impressed me. More recently she has been a pathfinder for more modern survey systems, and pound for pound is the most sophisticated survey unit in the RN.

“Gleaner is a real success story, and has more than proven her worth in charting the inshore zones around the UK and Channel Islands. All who have commanded or served in her take with them memories of huge affection for this sprightly old lady.”

In September 2003 HMS Gleaner was involved in an archaeological and geophysical survey of the Mary Rose wreck site and the Solent as part of work to establish dredging requirements for a possible new route into Portsmouth Naval Base for the Navy’s two new aircraft carriers.

This work will feature in a TV programme, called Wreck Detectives which is due to be broadcast on Channel 4 this year.

Prior to this HMS Gleaner spent 18 months away from Devonport conducting surveys off the coast of Scotland.

Gleaner is the sixth ship to bear the name, and has Battle Honours dating back to the Baltic in 1855. Three of her predecessors were also survey vessels, with the first being bought in 1809 and ordered to be ‘fitted out as a float light for Thornton Ridge, to be registered as a survey vessel by the name of Gleaner and established with guns and men.”

The fifth HMS Gleaner was a Halcyon-class minesweeper, built in 1938 and originally designated as a survey ship. But as war broke out she was undergoing conversion to a minesweeper in Plymouth and saw extensive service during World War II, gaining Battle Honours for the Atlantic, North Sea, the Arctic and Normandy.

The ship was eventually paid off into reserve in September 1946, and was broken up four years later.