Britain may once have had an empire on which the sun never set – but a study shows its true global reach was far more extensive than maps would suggest.

Throughout the ages, Britain has invaded almost 90 per cent of the world’s countries.

An analysis of the histories of almost 200 nations found that only 22 have never experienced a British assault.

These include Luxembourg as well as Guatemala, Tajikistan and the Marshall Islands in the Pacific.

The study – part of a new book, All the Countries We’ve Ever Invaded: And the Few We Never Got Round To – comes against the background of maps which show that at its height the Empire ruled over almost a quarter of the world’s population.

Author Stuart Laycock worked his way around the countries on the globe alphabetically to see if British forces had ever strayed into each territory.

However, only a very small proportion of his total list of invaded countries made up formal dominions of the Empire.

The remainder have been included if a military incursion was achieved through force, the threat of force, or by negotiation or payment. Raids by British pirates, privateers and armed explorers have been included if they were acting on the behalf or approval of the government.

Therefore, many countries that once formed part of the Spanish empire and seem to have little historical connection with the UK, such as Costa Rica, Ecuador and El Salvador, made the list because of the repeated raids they suffered from state-sanctioned British sailors.

The earliest invasion launched from the British Isles was an incursion into Gaul, northern France, at the end of the second century. Clodius Albinus led an army, thought to include many Britons, across the Channel in an attempt to seize the imperial throne. The force was defeated in 197AD at Lyon.

Other invasions highlighted in the book include that of Iceland in 1940 after the neutral nation refused to enter the war on the Allies’ side. The invasion force, of 745 marines, met with strong protest from the Iceland government, but no resistance.

Mr Laycock, who has previously published books on Roman history, began the two-year research after being asked by his 11-year-old son, Frederick, how many countries the British had invaded.

“I was absolutely staggered when I reached the total,” he said. “I like to think I have a relatively good general knowledge, but there are places where it hadn’t occurred to me that these things had ever happened. It shocked me.

“On one level, for the British, it is quite amazing and quite humbling, that this is all part of our history, but clearly there are parts of our history that we are less proud of. The book is not intended as any kind of moral judgment on our history or our empire. It is meant as a bit of fun.”

The only other nation which has achieved anything approaching the British total, Mr Laycock said, is France – which also holds the record for having endured the most British invasions.

He is now asking for the public help in listing more British invasions. Mongolia is listed as never been invaded, but Mr Laycock believes it could have been.