Protesters gather outside Russian Embassy following Alexei Navalny’s death

Images of the 47-year-old were left alongside a number of floral tributes.

Those gathered chanted “Putin is a killer”, and held up signs with slogans including “Putin will never stop killing”, “We are Navalny”, and “Don’t give up”.

At one point, members of the crowd held up their phone lights towards the embassy in unison.

A man at the protest, who did not wish to be named, said he wanted to be able to love his country again.

“I want Russia to be a country that is respected all over the world,” he continued, “I want to love my flag.”

“But today it’s not possible because the flag represents the war.”

Tearful speakers gave speeches in both Russian and English using a loudspeaker.

“Today we stand together to remember Alexei Navalny,” one said.

“Navalny leaves behind a family.

“His death is another painful example of cruelty and injustice under Putin’s rule.

“Let’s raise our voices and demand justice. Let’s show Putin he won’t make us silent.”

A British woman told the crowd: You’re not alone, I’m British and I stand here with my Russian brothers and sisters.

“Alexei Navalny stood for the real Russians, we love the real Russians and we mourn him.”

Russia’s federal prison service said in a statement that Mr Navalny became unwell after a walk on Friday and lost consciousness.

An ambulance arrived, but the politician and anti-corruption campaigner died despite attempts to resuscitate him, the agency said.

Britain has joined other western countries in condemning Russian President Vladimir Putin.

UK Foreign Secretary Lord David Cameron said there should be “consequences” for the Moscow leader.

Mr Navalny, who campaigned against official corruption and organised major anti-government protests, has been behind bars since January 2021.

He was arrested on his return from Germany, where he had been recuperating after a nerve agent poisoning that he blamed on the Kremlin.

Since the start of his imprisonment, the opposition leader had remained a thorn in the side of Mr Putin via scathing attacks that his associates continued to post on social media.

Kremlin spokesman Dmitry Peskov said Mr Putin was informed of Mr Navalny’s death and the prison service was looking into the matter in line with standard procedures.

When the Russian president has spoken about Mr Navalny previously, he has made it a point not to mention the activist by name, referring to him only as “that person” or similar in an apparent effort to diminish his importance.

He recently launched a presidential campaign for his fifth term in office, and is already the longest-serving leader in Moscow since Soviet dictator Joseph Stalin.

Mr Navalny’s wife, Yulia Navalnaya, has called for the international community to unite and hold Mr Putin’s regime responsible in the wake of Friday’s news.