UK travel restrictions: Are Portugal or Greece on the quarantine list?

They will also have to self-isolate for 14 days if they arrive in Wales from Gibraltar, French Polynesia or the Greek islands of Mykonos, Zakynthos, Lesvos, Paros, Antiparos or Crete.

The Joint Biosecurity Centre (JBS) - set up by the government to monitor coronavirus - works with the chief medical officers of each UK nation and advises which countries should be on its list.

The decision is generally made when 20 or more people out of every 100,000 in a country are infected over seven days. Other factors are also considered. These include:

Each UK nation sets its own quarantine list, although until recently these have generally been identical.

The Welsh government's new travel restrictions are the first it has introduced which differ. Earlier this week, Scotland announced it would require entrants from any part of Greece to quarantine.

Portugal was only removed from the list of countries from which travellers have to self-isolate on 22 August. At that time its coronavirus infection rate was below the key threshold of 20 cases per 100,000 people.

Cases have swiftly risen since then, and the country has posted a seven-day average of above 20 since the end of August.

However, Transport Secretary Grant Shapps tweeted on 3 September that England did not plan to add any countries to its quarantine list. So, Portugal is not on England's list of countries subject to quarantine rules.

But he warned that "14-day quarantine countries can & do change at very short notice".

Greece has seen an increase in cases in recent weeks, although this has stabilised at an average rate of 14 per 100,000 people.

Although this falls comfortably below the trigger level, Scottish ministers have said that a number of cases of the virus in Scotland have been traced back to travel from Greece. Justice Secretary Humza Yousaf said it posed a "significant risk to public health".

Wales's decision to quarantine travellers from some Greek islands follows a number of infections which have been linked to flights to Cardiff.

People entering the UK from most countries have to quarantine.

Restrictions have recently been reapplied to several countries which were previously exempt:

Travellers from countries that pose a "reduced risk" from coronavirus - in the government's eyes - are exempt.

The list for England currently includes:

There are separate exemption lists for Wales, Scotland and Northern Ireland.

Those entering the UK from the common travel area - the Republic of Ireland, the Channel Islands, or the Isle of Man - are exempt, as are the 14 British Overseas Territories.

Travellers not self-isolating when they are supposed to can be fined £1,000 in England, Wales and Northern Ireland, or £480 in Scotland.

They can be fined up to £3,200 in England if they do not provide accurate contact details, or £1,920 in Wales.

Travellers leaving the UK could still face restrictions - including quarantine - when they arrive in one of the exempted countries.

About half the countries and territories on the list have restrictions for arriving UK visitors. These include: