A total of 444 people were detected crossing the English Channel in small boats on Tuesday, the Ministry of Defence said.
This is the highest number of people since 562 were recorded on April 14 earlier this year.
Some 11 boats were detected on Tuesday, which suggests an average of around 40 people crossed the Channel per boat.
Priti Patel said preparation for the next deportation flight to Rwanda “begins now” after last-minute interventions by the European Court of Human Rights led to the cancellation of the initial flight.
Asylum seekers crossing the Channel
Andrew Matthews
The Home Secretary said she will “not be deterred from doing the right thing” as Government sources confirmed to the PA news agency that all migrants were removed from the plane which was set to take off on Tuesday night.
The European Court of Human Rights confirmed that it had granted an urgent interim measure in regards to an Iraqi national, and it is understood the Court was considering a number of further requests.
PA understands that the appeals were considered by an out-of-hours judge on papers, overruling the UK rulings.
A group of people thought to be migrants are brought in to Dover, Kent, by Border Force, following a small boat incident in the Channel
Andrew Matthews
It is understood that, at the present time, there is not a route for the Home Office to appeal against the decision.
The European Court has indicated to the UK Government that the Iraqi national should not be removed to Rwanda until three weeks after the delivery of the final domestic decision in his ongoing judicial review proceedings.
Ms Patel described the European Court of Human Rights intervention as “very surprising”, adding that “many of those removed from this flight will be placed on the next”.
She said the Home Office legal team is reviewing “every decision made on this flight”, and that preparation for the next flight “begins now”.
Following the grounding of the flight on Tuesday night, Ms Patel said: “Earlier this year, I signed a world-leading Migration Partnership with Rwanda to see those arriving dangerously, illegally, or unnecessarily into the UK relocated to build their lives there.
“This will help break the people smugglers’ business model and prevent loss of life, while ensuring protection for the genuinely vulnerable.
“Access to the UK’s asylum system must be based on need, not on the ability to pay people smugglers."