After practising diving on a downed WW2 fighter in the harbor entrance, the two dive teams headed down the coast to the site of Hermes' wreck.

Although there were aircraft carriers before Hermes, they started life as other types of ship.

Hermes was designed and built from the outset as a carrier, spending most of her career in the Mediterranean and Far East between the world wars.

Even though she was reduced to a training ship in 1938, the onset of war forced a return to front-line duties.

In 1942, she was sent to the Indian Ocean to support he Allied invasion of Madagascar.

When Japanese bombers threatened the port of Trincomalee in the north of the island, Hermes sailed to escape them.

Salvation was short lived. The carrier and her Australian escort, destroyer HMAS Vampire, barely got 65 miles before she they were pounced upon about 20 miles off the port of Batticaloa.

More than 80 Japanese dive bombers escorted by nine Zero fighters attacked, opposed by just half a dozen sluggish RAF Fairey Fulmar fighters and the anti-aircraft gunners on both ships.

Hermes succumbed in just 20 minutes. Hit 40 times she sank taking 307 men down with her.

The bombers then turned their attention to Vampire, breaking the ship in two; amazingly, just eight destroyermen were killed.

Hermes' wreck lies 60 metres down, which meant only one section - the bilge keel - was accessible for the diving teams.

"This is the first time that Royal Navy personnel have been able to pay their respects in such a way in the 75 years since Hermes was tragically sunk," said Chief Petty Officer Ward Peers, second-in-command of Fleet Diving Unit 2.

"Laying the ensign was a great honour for everyone involved. Being able to dive on such a huge piece of British military history is a huge achievement and we are extremely grateful for the opportunity given to us by the Sri Lankan Navy."

Fellow diver Lieutenant James Preston said it had been "a unique opportunity" none of team would forget.

"We're proud to have paid respect to the lost sailors on HMS Hermes - this visit will form a proud part of the team's history," he added.

"There was a lot of black coral on the hull, but not much more - the hull was in great condition and appeared strong with little corrosion.

Beyond diving on Hermes' wreck, the week with the Sri Lankan Navy should pave the way for more co-operation between the two navies and the diving arms in particular, with the Brits hoping to offer training courses for their Commonwealth colleagues in due course at the Defence Diving School on Horsea Island in Portsmouth.