IT soars 130 feet into the air and stands guard over Southampton Water and the Solent, some of the busiest waterways and shipping lanes in the country.

Calshot Tower, which has been a distinctive landmark for almost 40 years, now has the distinction of being a “Declared Facility’’ for the Coastguard’s Maritime Rescue Co-ordination Centre in the Solent area.

The station’s newly bestowed status means the structure can now be officially recognised as part of the Maritime Search and Rescue emergency services.

Manned by volunteer members of the National Coastwatch Institution (NCI), Calshot Tower sits on Hampshire County Council land, is owned by the Crown Estate and is leased to Associated British Ports, owners and operators of Southampton docks, who use radar equipment positioned on the roof.

With its motto Eyes Along the Coast the mission of the NCI is to Spot, Plot and Report.

l Spot: The NCI maintains a continuous visual watch from Ryde Steeple to the south east, Cowes to the south and from Fawley across to Netley , north of the lookout during daylight hours.

l Plot: Identify the location of any incident so it can be plotted quickly on an Admiralty Chart or Ordnance Survey Map, when reporting to the authorities.

l Report: Alert the coastguard at Leeon- the-Solent to co-ordinate any emergency action.

Just short of Southampton’s Civic Centre clock Calshot Tower has a watchroom with a 360-degree panoramic view into the Solent, with Fawley oil refinery at one end and the Isle of Wight at the other.

On a clear day, once at the top of the 100 steps, which have a steep incline, views stretch across to Cowes and Yarmouth on the Isle of Wight, as well as Portsmouth’s Spinnaker Tower.

Back in the early 1990s cuts in funding resulted in Calshot Tower being closed down for more than 20 years until it was restored to its former glory by local NCI members.

Today Calshot Tower is manned 365 days of the year throughout the daylight hours.

It was in January 2010 when the NCI held a recruiting event at the Waterside Sports and Social Club in the hope of attracting 20 or 30 volunteer watch keepers, but were overwhelmed by more than 100 people.

Volunteers come from all walks of life with a number of watch keepers having no previous maritime experience.

A spokesman for the NCI said: “It makes no odds at all as to whether you are a master mariner or the local postman, the most useful assets are a sharp pair of eyes and inquisitive nature.’’ The Calshot Tower branch of the NCI recently passed a demanding assessment, which gave them the status of a “Declared Facility’’. To celebrate this achievement chief coastguard Peter Dymond will visit the Calshot Tower next Tuesday to congratulate the volunteers and officially present a certificate confirming its role with the rescue services.

Calshot Tower stands next to an ancient castle, occupying a strategic position on the eastern entrance to Southampton Water. The geography here is perfectly suited for the location of a gun battery as the deep water shipping channel runs very close to the shore at this point.

Following Henry VIII’s split with Rome and his subsequent divorce from Catherine of Aragon threat of invasion was posed by a combined French and Spanish fleet. To counter this fear Henry commissioned the building of a string of coastal fortifications stretching from south Wales to the River Humber in the north east and Calshot Castle was one of these.

Finished in 1540 Calshot Castle was designed specifically as a base for a large amount of artillery but also to repel an attack.

Henry’s forts marked a significant change in English castle building as medieval castles, although big, bold and imposing, were easy target for 16th century cannon. Walls and parapets of the new smaller, squat castles, such as the one at Calshot, were curved or circular and immensely thick, enabling them to absorb and deflect incoming enemy shot.

Dramatic changes to the surrounding area occurred between the two world wars as it first became the Calshot Royal Naval Air Station and then the Royal Air Force School for Naval Co-operation and Aerial Navigation.

During the Second World War quick firing guns were re-mounted on the castle roof and additional searchlights were installed. Calshot RAF Air Station had become a centre for the maintenance and repair of seaplanes.

When the RAF station closed in 1953 Calshot Castle reverted back to providing coastguard accommodation until their adjacent new tower was completed. At that time, English Heritage took over the guardianship of the castle, restoring it to its former appearance pre-1914.