The death toll from the London Bridge attack has risen to eight as pressure on British authorities intensified amid new questions about how the terrorists slipped through the net.

Police searching for a French man missing since Saturday recovered a body from the River Thames on Tuesday night.

Xavier Thomas, 45, is thought to have been struck by the terrorists’ van on the bridge and witnesses reported him being thrown into the water.

London terror attack: Key locations London terror attack: Key locations (PA graphic)

The body was recovered near Limehouse, downstream from London Bridge, at around 7.45pm on Tuesday by specialist officers from the marine police unit.

French President Emmanuel Macron said a third French victim had been identified among those killed in the attack, adding: “We are paying a heavy cost in these attacks.”

Other victims believed to be dead are a Briton, a Canadian, a Spaniard and two Australians.

Key numbers on UK terror suspects graphic(PA graphic)

Controversy over the UK’s counter-terror efforts spread to border security after claims emerged that one of the perpetrators was let into the country despite being on a security watch list.

Youssef Zaghba is said to have told Italian police “I’m going to be a terrorist” when he was stopped trying to travel to Syria last year.

Prosecutors in Italy say there was not enough evidence to arrest or charge the 22-year-old when he was intercepted at Bologna airport.

However, unconfirmed reports suggest he was placed on the Schengen Information System (SIS II), a vast database of alerts about individuals and objects of interest to EU law enforcement agencies. It contains information on thousands of people wanted under the European Arrest Warrant, as well as suspected foreign fighters.

Alerts are made available in the UK through the Police National Computer and to Border Force officers at immigration controls.

Authorities are facing pressure to detail whether an alert was flagged about Zaghba when he came into the UK and whether he was stopped at the border.

Terror-related arrests in 2016 - reasons graphic(PA graphic)

The Home Office has not commented as there is an ongoing police investigation, while Scotland Yard has said Zaghba, who lived in east London, was not a police or MI5 subject of interest.

Questions over the extent to which the terror gang were known to security services have been mounting since it was revealed another of the attackers, Khuram Shazad Butt, 27, had been investigated in 2015.

Scotland Yard has confirmed that Butt was known to police and MI5 but said there was “no intelligence to suggest that this attack was being planned” and the probe “had been prioritised accordingly”.

The revelation meant perpetrators in all three of the terrorist outrages to hit the UK this year had been on the radar at some point.

The van used by the terrorists at London Bridge and Borough MarkerThe van used by three attackers in the London Bridge and Borough Market terror attacks (Jonathan Brady/PA)

Zaghba, Pakistan-born British citizen Butt and Rachid Redouane, 30, who claimed to be Moroccan-Libyan, launched a rampage around London Bridge and Borough Market on Saturday night.

Police have said Redouane was not known to security services. Butt and Redouane both lived in Barking, east London.

The rampage was brought to an end when the trio were shot dead by armed police eight minutes after the first emergency call.