Actors Jude Law and Kevin Spacey have joined more than 100 protesters calling for freedom of expression and an end to the dictatorship in Belarus.
The demonstration began outside public relations consultancy firm Grayling, in central London, with the protesters calling for the company to end its business within the former Soviet republic.
Law, who marched in support of dissident theatre group Belarus Free Theatre (BFT), said: "Freedom of speech is not just about artistic expression but also about fundamental freedoms.
"We have the opportunity in this country to protest, to be heard and to use our freedom of speech. It's our responsibility, therefore, that we speak for those who are less fortunate, especially as fellow Europeans.
"One would hope that this dictator will internationally be recognised for what he's doing, the tyranny that he's forcing people to live under."
The demonstrators then marched to the House of Commons where BFT, whose members have been targeted and imprisoned for speaking out against the government of dictator President Alexander Lukashenko, were to perform.
Spacey, who is artistic director of the Old Vic theatre company in London, spoke of his admiration for BFT after seeing the group perform in New York.
"I don't think I have ever sat in a nice, comfortable theatre seat and read a programme in which every single member of a theatre company has either been arrested or beaten or jailed or attempted to be silenced or lost their jobs because they have been part of a peaceful protest."
The American Beauty actor said he has just discovered that his own films and those of Law have now been banned in Belarus because of their involvement with the protests.
"They can ban as many films as they want but they will never be able to ban the Belarus people's right to fight for their freedom and their voices to be heard, and that's what this protest is about."
© Press Association