The identities of the 18-year-old and 21-year-old, being held on suspicion of terrorism offences, are yet to be officially revealed but it has emerged that both are refugees who had lived in the same foster home in Sunbury, Surrey, south-east England, which has been the focal point of police raids and searches over the weekend.
The younger man arrested at Dover ferry port on Saturday morning is an Iraqi refugee and the 21-year-old arrested later in the day has been named locally as Yahyah Farroukh, a Syrian refugee fostered by the same elderly couple from Sunbury – Penelope and Ronald Jones.
With the arrest of the suspects, the UK Home Secretary Amber Rudd announced that the country's terror treat level, which had been raised to its highest at "critical", would be lowered back to "severe" as "sufficient progress has been made" into the investigation.
"There is still much more to do but this greater clarity and this progress has led JTAC – the independent body that assess threat – to come to the judgement that an attack is no longer imminent," said Metropolitan Police Assistant Commissioner Mark Rowley, the UK’s National Lead for Counterterrorism Policing.
"The military support we have had in place under Operation Temperer will start to phase out as we move through the coming week," he said.
Farroukh was stopped by Metropolitan Police officers outside a fried chicken shop in the Hounslow area of west London on Saturday night, where searches are still ongoing.
Officers were also searching an address understood to be Farroukh's current home in Stanwell, Surrey, close to Heathrow airport.
The Joneses have been respected foster parents for almost 40 years and looked after up to 300 children, including eight refugees.
"One thing I understand is that he (the 18-year-old) was an Iraqi refugee who came here aged 15 – his parents died in Iraq," said Ian Harvey, Leader of Spelthorne Borough Council, which covers the Sunbury area.
Of the other suspect, he added: "I think it is widely known that this person who lives at (the Stanwell) property was a former foster child at the property which was raided".
According to a Facebook profile thought to belong to Farroukh, he is originally from Damascus, in Syria, and studied English for speakers of other languages at West Thames college, near the Stanwell property.
The profile also claims that he worked for an events company in London.
Meanwhile, CCTV footage has emerged of a man in a red cap in Sunbury carrying a Lidl supermarket bag, similar to the one the improvised explosive device was hidden in when it exploded on a Tube train in west London's Parsons Green station on September 15 morning, injuring 30 people.
The man was seen on camera leaving a house which police later searched.
A key aspect of the investigation has focused on CCTV, with officers combing through footage to establish who planted the device, and when and where it was placed on the train.