Easter getaway travellers have been warned of travel chaos due to enhanced security checks in the wake of the Brussels attacks.
Downing Street said there would be an increased police presence at ports, airports, underground stations and international railway stations, as well as enhanced border checks.
A spokesman said: "As a result, travellers over the Easter weekend may experience some limited delays to their journey and should check the advice of travel companies before starting their journeys."
Earlier, the Home Secretary said people should leave plenty of time for their journeys, especially if heading to the Channel ports.
Speaking in the House of Commons, Theresa May added that the United Kingdom needs to remain vigilant in the wake of the attacks.
More than 34 people were killed and more than 130 wounded in a pair of coordinated suicide attacks at Zaventem Airport and Maalbeek metro station in Brussels on Tuesday.
"Because we have extra checks - particularly for example at the Channel ports - it maybe that people may experience delays that they otherwise would not have done," May said. "People should ... look at making sure they have ample time when they are travelling."
She added that the Foreign Office had updated its website for travel advice and would continue to do so.
The warning comes after a number of engineering works had been announced, disrupting swathes of the networks this weekend starting from Good Friday on 25th March to Easter Monday on the 28th March.