Igor Sergunin was the only one of the three to admit the charge, according to independent reports, and was given a lighter sentence of three-and-a-half years.

Alexei Liptser was jailed for five years in a penal colony and Vadim Kobzev was given five-and-a-half years.

Kobzev’s own lawyer, Andrei Grivtsov, said the evidence against them amounted to illegal invasion of privacy.

“They’re not allowed to eavesdrop on meetings between a lawyer and a client in a penal colony in principle – there’s a direct legislative ban,” he told BBC Russian.

The three lawyers were put on trial close to the penal colony in Pokrov, where Navalny was initially sent when he returned to Russia in January 2021, having survived a nerve agent attack that he blamed on Russian leader Vladimir Putin.

The Kremlin denied the allegation and Navalny remained in Russian penal colonies until his death, north of the Arctic Circle and 1,900km (1,200 miles) north-east of Moscow.

His widow, Yulia Navalnaya, blamed Putin for his death, which authorities put down to “sudden death syndrome”.