Parsons Green train bombing

Four other attacks occurred in England in the months preceding the bombing: the Westminster attack, the Manchester Arena bombing, the London Bridge attack and the Finsbury Park attack.[12] According to the BBC home affairs correspondent Dominic Casciani, along with the Parsons Green train bombing and police having foiled at least seven 'significant plots', this makes it "the most sustained period of terror activity in England since the IRA bombing campaign of the 1970s."[13]

Map of the station area

A homemade bomb partially exploded on an eastbound District line train at Parsons Green Underground station, in West London.[14] The District line train was packed with commuters and school children.[15] Witnesses described seeing a fireball in the rear carriage of the packed rush-hour train. Numerous passengers were reported to have suffered flash burns. Others received crush injuries in the rush to leave the scene. Thirty people received medical treatment for their injuries, 19 of whom were taken to hospital by ambulance and the remainder self-presenting at hospital.[16]

The device had been left in a white plastic bucket inside a shopping bag. Wires were hanging out, as well as a black towel. Reports also indicate the device had a timer attached[17] and was packed with knives and screws.[18] According to Ben Wallace, the security minister, the bomb contained the triacetone triperoxide explosive (TATP), the same explosive used in the 2005 London Underground bombings and the November 2015 Paris attacks.[19] The explosive is known to be very unstable, which may have led to critical errors in the construction of the bomb, such that it only partially exploded. According to Chip Chapman, former head of counter-terrorism at the Ministry of Defence, "This absolutely didn't function properly because… 1 ounce (30 g) of TATP is enough to blow car doors off".[19]

The Metropolitan Police Counter Terrorism Command led the investigation into the attack.[24] According to the Metropolitan Police, “hundreds of detectives” were involved in the investigation.[25] Investigators reportedly linked the attack to Islamic extremism and considered feasible a network of individuals involved in such plans.[26] The Metropolitan Police launched a manhunt for one, possibly two, suspects.[27]

On 16 September, Kent Police arrested Ahmed Hassan at the Port of Dover on suspicion of a terror offence.[28] The port area was partially evacuated and a number of items recovered by the police.[29] Later that day, police raided, and searched a house in Sunbury, Surrey.[30] Hassan was not named initially, but was identified by media reports as an 18-year-old Iraqi orphan refugee[31] who had been referred to a governmental anti-extremist programme.[32]

Seven men were arrested in total during the investigations. Later on 16 September, a man was arrested in Hounslow, west London,[33][34] A third man, a 25-year-old, was arrested in Newport, south Wales, on 19 September and an address in Newport was searched.[32] The seventh and final arrest took place on 25 September in Cardiff. On 21 September the second arrestee was released without charge.

On 22 September, Hassan was charged with attempted murder and causing an explosion likely to endanger life or cause serious injury. He appeared in court the following day and was remanded in custody, to appear at the Old Bailey on 13 October.[18] The other six arrestees were released without charge.[35][36]

Ahmed Hassan pleaded not guilty to the charges. His trial took place on 5–16 March 2018 at the Old Bailey. The Crown Prosecution Service (CPS) indicated that Hassan had not conveyed his motive for the attack and that, perhaps due to his destruction of electronic devices, there was no evidence of ISIS being an inspiration.[37] On 16 March, he was found guilty by a unanimous jury.[38] On 23 March, he was sentenced to life imprisonment with a minimum of 34 years; he will be eligible for parole on 23 March 2052.[39] The sentence reflected the court's belief that Hassan had lied about his age and was in fact older.[40] It has been claimed, in an article by Lizzie Dearden of The Independent, that the police missed or misinterpreted evidence indicating Hassan was inspired by ISIS.[41]

Ahmed Hassan arrived in the UK in late 2015 claiming to be under 18, at a time when the UK government had shortly before instituted more generous rules on accepting asylum applications from unaccompanied minors.[40] At a January 2016 immigration interview, Hassan told officials he had been in contact with the Islamic State of Iraq and Syria and been trained to kill. Hassan also stated during the interview that he blamed the United Kingdom for his father having died in Iraq.[42] While his asylum application was being processed, he was placed in foster care with a highly experienced elderly foster couple who were given no hint of his extremist links.[40]

• 7 July 2005 London bombings
• 21 July 2005 London bombings
• Cannon Street train bombing
• Bombings of Paddington and Victoria stations
• Green Park tube station bombing
• Bombings of King's Cross and Euston stations
• West Ham station attack