Royal Marines are poised to lead a 'Dunkirk-style' evacuation of thousands of UK nationals from the Middle East should Iran launch a missile strike on Israel.

Commandos have already conducted reconnaissance along the Lebanese coastline ahead of a potential maritime rescue mission.

Tonight, speaking exclusively to the Mail, Defence Secretary Grant Shapps confirmed he 'stands ready' to assist any Britons trapped in the region. 

The Foreign Office has already advised all UK citizens to leave Lebanon.

Tonight US National Security Council spokesman John Kirby said there remained a 'serious threat' of attack while it was reported that Iran had sent a message to Washington warning them against the involvement of US troops in the region.

Defence Secretary Grant Shapps on a visit to Catterick Garrison, in North Yorkshire, to tour the base and meet troops

The evacuation plans, codenamed Operation Meteoric, will be spearheaded by the UK's 'Green Berets' and supported by the Royal Navy and Royal Air Force. 

The Mail has been told a party of Marines from 30 Commando arrived in the region in recent days.

Operation Meteoric has been likened to Operation Dynamo, the evacuation of hundreds of thousands of allied soldiers from Dunkirk in 1940 when they were surrounded by German forces.

Israel and its allies remain braced for a huge Iranian response to the attack on its Syrian consulate earlier this month, which left 13 dead, including a senior Iranian commander.

While Israel has not claimed responsibility for the blast it is widely considered to have been behind it. 

Iran's response may also involve the heavily armed military group Hezbollah, which is based in Lebanon.

Tonight, intelligence reports suggested the retaliation could include more than 100 drones, dozens of cruise missiles and ballistic missiles.

Such a scenario would likely lead to civilian 'air bridges' shutting down – hence the need for a maritime solution.

Defence Minister Grant Shapps confirmed he 'stands ready' to assist any Britons trapped in the region

Commandos have already conducted reconnaissance along the Lebanese coastline ahead of a potential maritime rescue mission

The Royal Navy's new minehunting 'mothership', RFA Stirling Castle, which has recently arrived at its new home on the Clyde

The Mail has been told how the preparatory work behind Operation Meteoric was conducted by the Royal Marines' Surveillance and Reconnaissance Squadron (SRS). 

They studied stretches of the Lebanese coastline and selected potential locations for such a rescue mission.

Stranded civilians would be ferried from beaches in raiding craft to Royal Fleet Auxiliary (RFA) ships in the eastern Mediterranean.

While it is understood Iran is eager to avoid direct engagement with UK forces, RAF Typhoon jets based in Cyprus could provide 'top cover'.

Tonight Mr Shapps told the Mail: 'UK nationals in the region will be concerned by what Iran is threatening to do. So we stand ready to assist them. 

'There are plans, but they cannot be discussed for security reasons.'

Tonight the IDF confirmed around 40 rockets had been fired into northern Israel by Hezbollah fighters in Lebanon.