The sentence represents more than four years longer than the prosecution had asked, indicating the court's firmness in dealing with Mann.

Judge Carlos Mangue said the 55-year-old "had failed to show an attitude of regret", despite his apology before the court.

Mann acknowledged during the trial last week that he knowingly took part in the attempt to topple the government.

His lawyer, however, argued that Mann was a secondary player and not the author of the botched 2004 coup.

The judge upbraided Mann, saying he had shown little remorse and stressing that his role was far more significant than he was letting on.

Speaking to Channel 4 News about the verdict Mann said: "Well, I'll just have to push it." He said he did not know whether he would be able to appeal because he did not know "how it works here".

Equatorial Guinea held its first trial into the alleged plot in August 2004.

South African arms dealer Nick Du Toit was sentenced to 34 years in prison as a result of the case.

Sir Mark Thatcher, the son of former prime minister Baroness Thatcher, was given a suspended sentence in South Africa in relation to the funding of Mann's operation, though he has always denied any knowledge that a coup was being plotted.