The deal ensures a permanent footing for the Royal Navy in the oil-rich Gulf, Hammond said.

The Strait of Hormuz, which is the Gulf’s only exit and is bounded by Iran and Oman, is the route for 30 percent of world oil supplies carried by tanker ships.

The agreement will create Britain’s first fixed Gulf base since it pulled out of former imperial outposts commonly referred to as being “east of Suez” over four decades ago.

Four British mine-hunter warships are already based in Bahrain, and other British ships rely on facilities in the kingdom.

The base is expected to open in 2016.