After spending five years living as a fugitive, he was arrested in Kosovo in May.
However, attempts to bring him back the UK to face charges were thwarted when a Kosovan judge blocked the extradition order on the basis that his alleged crimes have expired in Kosovo, which has a 30-year statute of limitation.
On Sunday night, Scotland Yard announced that Fr Soper was arrested as he arrived back in the UK at Luton Airport from Kosovo.
A spokesman said he was “arrested on suspicion of nine offences of sexual assault committed over a period from 1972 to 1986”
In 2011, Lord Carlile of Berriew stripped monks of control at St Benedict's School, which offered a "heartfelt apology for past failures".
The peer said he hoped his decision to take powers away from Ealing Abbey would "set a template" for other schools.
In his inquiry into the sexual abuse, Lord Carlile outlined a catalogue of failures by the abbey to intervene as allegations of abuses came to light.
"I have come to the firm conclusion ... that the form of governance of St Benedict's School is wholly outdated and demonstrably unacceptable," he wrote.
"The abbot himself has accepted that it is 'opaque to outsiders'."
The report added: "In a school where there has been abuse, mostly - but not exclusively - as a result of the activities of the monastic community, any semblance of a conflict of interest, of lack of independent scrutiny, must be removed."