LONDON, July 22 (Reuters) – Britain’s failure to prevent Iran’s Revolutionary Guards from seizing a British-flagged oil tanker in the Strait of Hormuz shows the decline of the once mighty British navy.

The navy, which has one frigate and four mine sweepers in the Gulf, is now far too small to fulfil its global role, according to Tobias Ellwood, a defence minister.

Britain once had the most powerful navy in the world. But the size of the fleet has declined rapidly over recent decades – largely due to decades of spending cuts.

Here is a look at the size of the British navy:

* Britain spends more on defence than France, Germany, Italy, Spain or any other European Union country. The problem is that much of this is on the renewal of its nuclear programme and on two new expensive aircraft carriers, leaving conventional forces such as the navy short of surface ships.

* Britain has one frigate, HMS Montrose, and four mine sweepers on duty in the Gulf.

On any given day, about 15 to 30 large British-flagged ships travel through the Gulf, with up to three passing through the Strait of Hormuz.

A second frigate, HMS Kent, and a destroyer, HMS Duncan, are heading towards the region to replace HMS Montrose.

Britain simply does not have the naval resources in the region to escort every British-flagged merchant vessel through the Strait of Hormuz.

* Britain’s navy currently has 77 commissioned vessels, including six destroyers, 13 frigates and 10 submarines. The rest are primarily minesweepers, survey ships and other support vessels.

By comparison the navy had 138 ships and 33 submarines in 1990. So in the last three decades the navy has reduced the number of submarines, frigates and destroyers by more than half, according to Ministry of Defence.

Roughly half the ships are in routine maintenance or training at any given time. For example, the defence minister Stuart Andrew said in October four of the frigates will spend all of 2018 in port.

Several others are committed to small standing patrols, which leaves just a handful of vessels to respond to emergencies.

* The navy currently has one aircraft carrier. A second aircraft carrier is due to be commissioned next year. But they are much smaller than US aircraft carriers and slightly smaller than Russian and Chinese carriers.

A leak on the aircraft earlier this month forced the ship to return to port early.

* The Royal Navy has shed people faster than ships. Britain had 39,000 sailors in the navy in 2000. It now has a little more than 30,000.

In 1945 at the end of Second World War, the Royal Navy has 861,000 sailors, a number that fell to 128,000 in 1955 and 62,000 in 1991, according to the Ministry of Defence.

This has coincided with cuts to the defence budget, which has declined from over 4% of economic output in 1990 down to around 2% percent now.

* Britain’s shrinking navy is under intense pressure, facing the challenge of protecting its own waters when it is facing so many tasks in other parts of the world.

* From the mid 18th century the Royal Navy was the world’s most powerful navy. It was played a key part in establishing the British Empire. The United States overtook British naval mastery during World War Two.

As an island nation, the prestige of the navy, has played an important part of its national character. The navy helped Britain rule the waves, as the lyrics of the patriotic song “Rule Britannia” state.

* On D-Day in 1944, Britain was able to send more than 900 British warships across the English Channel to escort allied troops who would liberate Europe from Nazi Germany.

But after the cost of funding two world wars and abandoning its imperial role, Britain gradually began to down size the size of its navy.

(Reporting By Andrew MacAskill; editing by Guy Faulconbridge)