A 10-day mandatory hotel quarantine requirement for travellers arriving from 33 "red list" countries, including much of South America and southern Africa, as well as Portugal and the UAE, will come into effect on Monday (15 February).

Arrivals are required to pre-book their hotel quarantine and testing package before setting off at a cost to them of £1,750.

On Thursday, the website was taken down and replaced with a notice that read: "We’ll be back soon! Sorry for the inconvenience but we’re performing some maintenance at the moment."

The message was still live at shortly before midday on Friday.

Those arriving from non-red list destinations will also be subject to a more stringent testing regime during their mandatory 10-day quarantine at home requirement from Monday.

Besides a pre-departure test, arrivals will have to pre-book PCR tests for the second and eighth day of their quarantine at a cost of £210.

However, the testing portal was also down shortly before midday on Friday.

The gov.uk guidance page carried the following message: "Due to a minor technical issue, the link to the booking portal in this guidance will not be available until later today. Please return to this page later if you wish to make a booking."

Those failing to comply with any of the new requirements could face fines of up to £10,000, while any found to have lied about their travel history on their passenger locator fine to avoid hotel quarantine have been threatened with jail sentences of up to 10 years.