A major national security investigation has led to the arrest and charging of three suspected Russian spies in the UK

Bulgarian nationals, all defendants, were detained in February and have been remanded in custody ever since.

It is alleged that they knew that the documents they possessed were fake and therefore had “improper intent” to possess them.

The Russian security services are alleged to have employed them.

Among the documents are passports, identity cards, and other documents for the UK, Bulgaria, France, Italy, Spain, Croatia, Slovenia, Greece, and the Czech Republic.

An offence under the Official Secrets Act was suspected of being committed by the trio in February.

In September, they will answer bail to police officers from the Metropolitan Police, which has national policing responsibility for espionage.

Later in February, three of them were charged with violating the Identity Documents Act.

The following are among them:

• Orlin Roussev, 45, of Great Yarmouth, Norfolk, has been arrested

• Bizer Dzhambazov, 41, lives in Harrow, north-west London

• Katrin Ivanova, 31, of the same address in Harrow

Their appearance at the Old Bailey is scheduled for later this week. They remain in custody.

Living in suburban properties and working in a variety of jobs, the trio have lived in the UK for many years.

There is a history of business dealings between Mr Roussev and the Russian government.

After moving to the UK in 2009, he worked in financial services for three years.

He later owned a business involved in signals intelligence, which involves interception of communications or electronic signals.

He also claims to have served as an adviser to the Bulgarian ministry of energy in the past. Mr Roussev’s most recent address is a seaside guesthouse in Great Yarmouth.

Mr Dzhambazov and Ms Ivanova were described as a couple by former neighbors in Harrow.

On his online LinkedIn profile, Mr Dzhambazov describes himself as a driver for hospitals, while Ms Ivanova describes herself as a laboratory assistant for a private health institution.

After moving to the UK around a decade ago, the couple ran a community organization that provided services to Bulgarians, including introducing them to British culture and values.

Electoral commissions in London facilitate foreign citizens voting in Bulgarian elections, according to Bulgarian state documents online.

Their neighbours at two houses previously occupied by the couple said they brought round pies and cakes.

Detectives spent a significant amount of time searching their most recent home in Harrow, with a police presence visible for more than a week, neighbours said.

In January, the three defendants will stand trial at the Old Bailey in London. As of yet, they have not entered a plea to the charges.

It has been reported publicly that police are spending more time investigating suspected state threats and espionage, especially relating to Russia.

In recent years, Russian intelligence operations in the UK have been the subject of notorious incidents.

Using the deadly nerve agent Novichok, Russian operatives attempted to murder former double-agent Sergei Skripal and his daughter Yulia in Salisbury, Wiltshire, in 2018. They were treated in hospital and could have died, along with responding detective Nick Bailey.

A local woman – Dawn Sturgess – died later that year after being exposed to the nerve agent in a perfume bottle left in Wiltshire.

Assassins working for the Russian government poisoned former Russian intelligence officer Alexander Litvinenko in London in 2006.