London attack: Second man arrested in connection with Parsons Green Tube attack

Terror threat level is reduced to 'severe' after two men detained

Man seen walking with Lidl bag in Sunbury-on-Thames area on morning of explosion (ITV News)

A second man has been arrested by detectives investigating the terrorist attack at Parsons Green Tube station, the Metropolitan Police has said.

The 21-year-old man was arrested in Hounslow at around 11.50pm on Saturday under the Terrorism Act. He was taken to a south London police station and remains in custody.

Meanwhile, new footage, obtained by ITV News, shows a person carrying a large Lidl bag on the morning of the attack. The CCTV footage was reportedly filmed near one of the suspect's homes in Sunbury-on-Thames in Surrey, around 90 minutes before the explosion injured 30 people.

A spokesman for New Scotland Yard said: "We are aware of the footage. This is a live investigation and we will provide further updates as it progresses. Not prepared to discuss further at this time."

Forensic officers carried out a search of a property in Stanwell, Surrey, close to Heathrow Airport.

Following the two arrests, the Joint Terrorism Analysis Centre (JTAC) lowered the UK's terror threat level from critical to severe, meaning an attack is thought to be highly likely but not imminent.

After the attack on Friday morning, photos circulated online of the partially exploded device, which had wires protruding from a flaming bucket.

Assistant Commissioner Mark Rowley, the country's top counter-terrorism officer, said: “We are getting a greater understanding of the preparation of the device.

"There is still much more to do but this greater clarity and this progress has led JTAC - the independent body that assesses threat - to come to the judgement that an attack is no longer imminent."

An 18-year-old man was detained in the departure area of the port of Dover in connection with the attack on Saturday morning.

He was arrested by Kent Police under the Terrorism Act and remains in custody at a London police station.

Deputy Assistant Commissioner Neil Basu described the arrest as “very significant”.

A search was also carried out at a house in Sunbury-on-Thames, Surrey, at the home of foster care couple Penelope and Ronald Jones, who previously received MBEs for services to children and families.

The couple are said to be staying with friends for at least the next five days following the police raids, during which surrounding houses were evacuated by counter-terror officers, with residents told they had “one minute” to flee their homes.

Friends said the couple – who have been foster parents for almost 40 years and have taken in up to 300 children, including eight refugees – had an 18-year-old and a 22-year-old staying with them recently.

The latest arrest comes after Mr Basu said police were keeping an “open mind” over whether more than one suspect was involved in the bombing.

Thirty people were injured when the improvised device exploded during rush hour at Parsons Green station.

All but one of those injured in the explosion have been discharged from hospital, NHS England said.

Police have since identified 121 witnesses, of whom 100 have been spoken to, Mr Basu said.

A key strand of the investigation has focused on CCTV as officers comb through footage to establish who planted the device, and when and where it was placed on the train.