The family of a British man locked up in Ethiopia under the shadow of a death sentence will take a petition to Downing Street calling on the Prime Minister to seek his release.
Andargachew "Andy" Tsege, who is in his 60s, has been detained in the country since he was removed from an airport in Yemen in June 2014.
The father-of-three, who fled Ethiopia in the 1970s and sought asylum in the UK in 1979, had been a prominent critic of the country's ruling party.
He was sentenced to death in his absence in 2009 for allegedly plotting a coup - charges he and others deny.
He had previously been secretary general of Ginbot 7, a political opposition party that called for democracy, free elections and civil rights in Ethiopia.
Mr Tsege's partner and children are expected to be be joined by MPs including Emily Thornberry and celebrities such as comedian and actress Sara Pascoe as they hand in a 30,000-strong petition to Downing Street on Tuesday, human rights organisation Reprieve said.
In September, his nine-year-old daughter failed in a High Court bid to challenge the way the British Government is dealing with the case.
A judge ruled the challenge "unarguable" and said: "This claim serves no purpose whatsoever."
His family's battle to have him freed and returned to the UK led to the High Court application in London for judicial review.
Refusing permission to seek judicial review, Mr Justice Mitting said the Government's approach to dealing with the case was neither irrational nor unlawful.
In a one-day hearing, the Foreign Office was accused of taking a "manifestly unreasonable" approach by merely lobbying the Ethiopian authorities to provide fair treatment and "due process" for Mr Tsege through Ethiopia's judicial system.
The family also accused the British Government of unlawfully failing to treat the case as a kidnapping.