Sarah Wykes has also worked for Amnesty International and Oxfam

Sarah Wykes, of Cumbria, was arrested on suspicion of espionage in the province of Cabinda on 18 February.

She was later released on bail but was confined to a hotel by authorities as they prepared a case against her.

Last week the country's prosecutor general said Ms Wykes was free to fly home but she may still have to return as the claims have not been dropped.

The 41-year-old campaigner was investigating corruption in the oil industry for charity Global Witness when she was arrested.

'Traumatic experience'

A spokesman for the group condemned the actions of the Angolan authorities.

He said: "We are relieved that she is on her way back and we are now calling for the prosecution against her to be dropped as there is no basis for it.

"It has been a very traumatic experience for Sarah.

" It has been very difficult to get any information from the Angolan government about what she is alleged to have done."