Up to 100 Islamic State fighters could in theory attempt to return to Britain, a senior counter-terror officer has disclosed.
Deputy Assistant Commissioner Neil Basu emphasised that authorities are "absolutely waiting" for any militants who try to come back.
But he played down the prospect of all those who are technically eligible to re-enter the country doing so.
Security services estimate that around 300 individuals who travelled from the UK to take part in the conflict in Syria and Iraq remain in the region.
Mr Basu noted that not all of those are "mono-Brits", saying the number includes "a lot" of dual nationals.
In an interview published by the Combating Terrorism Centre at West Point, he said: "Like other countries, we operate on the principle that we don't want you back, and therefore we will deprive you of your British passport. And the Government has done that.
"Because of this, the ones who could come back are about a third of this 300 number.
"And for those among these who end up coming back, we are absolutely waiting for them. That's the bottom line."
The Home Secretary can deprive someone of their British citizenship if they are satisfied taking the measure is "conducive to the public good", such as in national security cases.
There are rules against rendering someone "stateless", and the power can only be used where the individual in question has dual nationality, or if there is a reasonable belief that they could acquire citizenship of another state.
Figures show that 36 deprivations of citizenship orders were made on the "public good" basis between 2006 and 2015. More up-to-date statistics are expected to be published in the coming weeks.
Unconfirmed reports have suggested Londoners Alexanda Kotey and El Shafee Elsheikh, who are suspected of being members of the IS group nicknamed "The Beatles" and were captured last month, were stripped of their UK citizenship.
Approximately 850 UK-linked individuals travelled to engage with the Syrian conflict, according to Government estimates.
Around half have returned, while 15% are believed to have died.
Mr Basu said the large majority of those who have come back did so "very quickly and early on" and are "not where the bigger threat lies".
The Metropolitan Police officer identified the possible return of "committed recruits" as the greater danger but predicted most would rather "fight on" than come back.
"As far as those who are still overseas are concerned, we have been making it very clear that this will be a very hostile place to come back to, and I do not think most of these foreign fighters will want to come back," he added.
Predictions of a "large reverse flow" as the so-called "caliphate" disintegrated have not materialised, he said, adding: "Instead, we are seeing just the odd person come back."
Mr Basu, the senior national co-ordinator for counter-terror policing, also highlighted how the IS ideology has been "diffused onto the internet".
He said: "The caliphate may have been defeated militarily, but it has now become a virtual network."
Calling for close co-operation from social media companies, he said: "They've got the brainpower, and they've got the resources, and they need to help."
Mr Basu also backed calls for the "hugely controversial" Prevent programme to be subject to independent review.