The Christmas tree in Trafalgar Square is the City of Oslo's traditional Christmas gift to the City of Westminster.

The first tree was brought over in 1947 as a token of Norwegian appreciation of British friendship during the Second World War. When Norway was invaded by German forces in 1940, King Haakon VII escaped to Britain and a Norwegian exile government was set up in London. To most Norwegians, London came to represent the spirit of freedom during those difficult years. From London, the latest war news was broadcast in Norwegian, along with a message and information network which became vital to the resistance movement and which gave the people in Norway inspiration and hope of liberation.

The tree has become a symbol of the close and warm relationship between the peoples of Britain and Norway. Norwegians are happy and proud that this token of friendship - probably the most famous Christmas tree in the world - seems to have become so much a part of Christmas for Londoners.

The tree itself, a Norwegian spruce (Picea abies), is chosen with great care. Selected from one of the forests surrounding Oslo, it is earmarked for its place of honour in London several months, even years, in advance. The tree is usually 20 to 25 m (70 ft) in height and anything between 50 and 60 years old. The Norwegian foresters who tend it with loving care describe it as "the queen of the forest".

It is cut down one day in November. Most years, the first snow will have just fallen to brighten the otherwise dark forest. The cutting down ceremony is quite a grand occasion, with the mayor of Oslo and the British ambassador to Norway usually present.

The tree is then carried - free of charge - across the North Sea by a Fred. Olsen cargo ship sailing from Oslo to Felixstowe. It takes six or more men to handle the tree. They are specially contracted to haul it from the docks to that part of Trafalgar Square which is allocated year after year to the Norwegian Christmas tree.

It takes several hours to put the tree up. Scaffolding is erected, the tree is winched up, and the base of its trunk pushed into four feet of soil and sand beneath the grey stone slabs. A dozen or more wooden wedges are driven in to make it secure. There is no other form of support. The tree stands there again as it did in the forest.

This is no ordinary Christmas tree. There cannot be many Christmas trees that have to be positioned in such a way that they will stand up to the prevailing south-westerly winds. One year, the wind took off three metres of the tip of the tree. (That was just bad luck and could not be helped.) But when, on another occasion, the tree snapped neatly in half as it was being unloaded from the ship, the people of Oslo came to the rescue and produced a replacement tree.

The ceremony of the switching-on of the lights usually takes place on the first Thursday in December. The scene is familiar to most of us. There is a band, and trumpeters are playing. A choir sings Christmas carols as the Lord Mayor of Westminster arrives with his party. The floodlighting of the nearby National Gallery is especially dimmed for the occasion. The Christmas tree comes alive at the flick of a switch, into a sparkling, twinkling mass of lights. In line with Norwegian tradition, the lights are all white, the electrical bulbs being the twentieth-century equivalent of candlelight.

A crib provided by the Vicar of St. Martin-in-the-Fields is erected on the west side of the Square. It is dedicated at a special service on the Sunday after the lighting-up ceremony. The passing public may stop on their way home from work and join the carol singers every night until Christmas. During the carol singing, donations to selected charities are collected by volunteers.