An investigation into a Russian spy cell in the UK has found that three of those convicted previously attended Brexit debates in the Palace of Westminster in 2016. Three Bulgarian nationals, Orlin Roussev, Biser Dzhambazov and Katrin Ivanova, were convicted of spying for Russia, with at least two attending the debate in a committee room in parliament.

Photographs on social media show them in a room with dozens of people debating the merits of leaving the European Union. Their presence in the photographs has been confirmed by people who knew them at the time after being uncovered by the BBC. Acquaintances were able to confirm the presence of Roussev and Dzhambazov, whilst it is thought to be likely that Ivanova was also present.

It is not known what contribution, if any, the spies made to proceedings, with organiser Baroness Brown of Silvertown telling the BBC that she had no memory of the group.

A parliamentary spokesperson said Parliament was a public building but that security processes were "robust".

There is no suggestion that Baroness Brown or any parliamentary authorities are guilty of any wrongdoing.

Katrin Ivanova was convicted of offences alongside Tihomir Ivanchev and Vanya Gaberova between August 2020 and February 2023, following a four-month trial at the Old Bailey in London.

The leader of the spy cell, Roussev, had previously pleaded guilty to spying charges, as had his right-hand man, Dzhambazov, and another man, Ivan Stoyanov.

The group conducted intelligence gathering operations across Europe, which targeted enemies of the Russian regime, including journalists, dissidents and political figures.

Their activities were directed from Russia by Jan Marsalek, an Austrian former finance executive, who is understood to have fled criminal charges in Germany and is hiding in Moscow.

Authorities recovered a tranche of communications between Marsalek, a Russian intelligence asset and Roussev, with the pair known to have been in communication prior to the Brexit debate in Westminster in May 2016.

It is believed that the group included two more women who are currently based outside the UK and remain free.

The six convicted members of the group are due to be sentenced later this week.