Sailing too close to Iranian waters has repeatedly proved to be fraught with danger.

Although it is yet to be confirmed where the Kingdom Of Bahrain yacht was located when it was detained, British servicemen have been captured by Iranian authorities in its waters before.

Iran took 15 British service personnel hostage on March 23 2007 and held them for 13 days.

The Royal Navy sailors and Royal Marines, from the frigate HMS Cornwall, were taken at gunpoint during a routine search of a cargo ship.

Iran alleged the frigate had strayed into Iranian territorial waters in the disputed Shatt al-Arab waterway but the Ministry of Defence denied the allegation and said the ship was in Iraqi waters.

Footage of crew members was broadcast by Iranian television during their kidnap ordeal.

The Iranian president agreed to pardon and free them on April 4 2007.

In July 2004, eight British servicemen were seized and detained in the same troubled waters after three patrol boats were said to have strayed into the Iranian side of the waterway.

The capture sparked a tense stand-off.

The men were blindfolded and held for three days during which time they were paraded on Iranian TV.

And in 2006 four British soldiers, including Staff Sergeant Sharron Elliott, were killed when a bomb exploded near their boat on the waterway in Basra City on Remembrance Sunday.