Retired Major Nils Egelien of the Royal Norwegian Guards said: "It all started in 1961 when the King's Guard of Norway came to the military tattoo and we were very very interested in the king penguins.

"In 1972 we came back again and adopted a king penguin in the name of Nils Olav and the rank of lance corporal.

"In 1982 he was a corporal, in 87 a sergeant and in 1993 a regimental sergeant major."

Keeper Rob Thomas said that, if Nils Olav was aware of his status, he did not show it.

Bronze gift

He said: "They're a pretty quiet lot. I think that any one penguin would soon be put down by the others if it tried to assert its superiority over the others.

"All the penguins here are used to the company of humans. It is a very public exhibit, if you like, or they have the space to get away if they want to get into a more solitary situation.

Major Egelien said that the new rank of Nils Olav could not be revealed until the ceremony had taken place.

They are having a bronze statue made of the penguin for the king of Norway.

The penguin which was promoted is not the original Nils Olav. He died in 1987 and was replaced by a two-year-old penguin.