Which areas of south west Herts are in Tier 3 - and which are not?

Health Secretary Matt Hancock delivered the news, which will come as a blow to thousands of people, in the House of Commons today.

It forms part of the tier review that was not expected to be announced until Wednesday.

But due to a surge of cases in London, Essex, and parts of Hertfordshire, the announcement was brought forward.

Watford, Hertsmere, Three Rivers, and Broxbourne are the four areas of Hertfordshire that will move into Tier 3 from Wednesday.

This means pubs and restaurants will close except for delivery and takeaway.

In Watford, Three Rivers, and Hertsmere, this includes:

Watford borough

All of Watford, including Garston and Oxhey.

Hertsmere

Borehamwood, Bushey, Bushey Heath, Potters Bar, Radlett, Aldenham, Shenley, Letchmore Heath, South Mimms, Ridge, Patchett's Green

Three Rivers

Rickmansworth, Abbots Langley, Leavesden, Croxley Green, South Oxhey, Chorleywood, Carpenders Park, Maple Cross & Mill End, Bedmond, Hunton Bridge, Sarratt, Moor Park and parts of Kings Langley and Nash Mills.

Where has avoided Tier 3?

St Albans, Harpenden, and Hemel Hempstead will not be in Tier 3. They fall within the districts of St Albans and Dacorum.

Villages very close or near borders of boroughs now in Tier 3, but have just escaped and remain in Tier 2, include Bovingdon, Chiswell Green, Park Street, How Wood, Bricket Wood, London Colney, Apsley.

Kings Langley and Nash Mills straddle the boundary of Three Rivers and Dacorum. Those areas in Three Rivers will be in Tier 3.

St Albans District Council leader Chris White tweeted that St Albans had avoided Tier 3 "by the skin of its teeth".

However, the rest of Hertfordshire could still potentially follow Watford, Hertsmere, Three Rivers, and Broxbourne into Tier 3, the leader of Hertfordshire County Council has warned.

Those living in Tier 3 must avoid any "unnecessary travel" into Tier 2 areas, Matt Hancock said.

Cllr David Williams said: "The Government has announced that four of the 10 district council areas in Hertfordshire will move to the ‘Very High’ level (Tier 3) of local Covid alert categories from 00:01 on Wednesday 16 December.

"The other six district council areas in Hertfordshire will remain at ‘High’ alert level (Tier 2) but will be included alongside all other areas in England as part of the Tier review planned for Wednesday 16 December."

He added: "We recognise the concerns that this escalation will prompt with both residents and businesses and the additional restrictions and tougher rules that this involves.

"The Government has taken this decision in response to the very significant increase in case numbers across the county and due to the proximity of these four district areas to north London and Essex where infection rates have also been growing significantly.

"We must all now redouble these efforts, particularly as we all plan for how we will follow the rules over the Christmas and New Year period including, the ‘Christmas bubble’ guidance."

Cllr Williams confirmed the council is developing plans to "significantly increase" testing capacities across the county to try and identify more people who may be Covid-positive but asymptomatic and therefore inadvertently spreading the virus.