The first small boat migrants have been detained for removal to France under the new 'one in, one out' scheme.
The Home Office confirmed Channel arrivals were held after they were brought into Dover yesterday.
It did not disclose how many migrants had been held.
But the detentions come amid huge concerns that human rights challenges and other legal actions could delay migrants being sent back for months, as well as scepticism over the narrow scope of the scheme.
Migrants selected for removal will be held in Home Office detention facilities rather than being sent to live in taxpayer-funded asylum hotels.
