Everything you need to know ahead of tomorrow's big reveal on which tier Hemel Hempstead goes into

Prime Minister Boris Johnson revealed on Monday there will be a return to the tiered Covid National Alert system after the current national lockdown ends on December 2.

Dacorum and Hertfordshire were both in the lowest tier — medium risk — before the lockdown was announced on November 2 but the number of cases in the county has continued to rise sharply.

The PM has also suggested that there will be more areas put into higher tiers this time as previous restrictions were not tough enough.

The Government says it will announce what tier Dacorum will be placed in tomorrow (Thursday) but some rules will apply to all areas. Here's what we know:

What will be looked at to determine Dacorum tier?

The Government will look at the latest data, including the impact of current measures. Decisions will primarily be based on five key indicators:

1. Case detection rates in all age groups

2. Case detection rates in the over 60s

3. The rate at which cases are rising or falling

4. Positivity rate — the number of positive cases detected as a percentage of tests taken

5. Pressure on the NHS, including current and projected occupancy of hospital beds

Whatever tier Dacorum is in, everyone:

- MUST wear a face covering in most indoor public settings and on public transport, unless they have an exemption

- SHOULD follow the rules on meeting others safely

- SHOULD attend school or college as normal, unless they are self-isolating. Schools, universities, colleges and early years settings remain open in all tiers

- SHOULD walk or cycle where possible, plan ahead and avoid busy times and routes when travelling

- MUST follow the gathering limits at their tier except for in specific settings and circumstances. These exemptions are detailed at the end of this guidance.

In all tiers, the following businesses and venues can remain open but must remain Covid-secure:

- Essential and non-essential retail, including indoor and outdoor markets and car boot sales

- Certain leisure and sporting facilities such as gyms, sports courts and facilities, leisure centres, fitness and dance studios, golf courses, swimming pools, riding centres, outdoor playgrounds - subject to relevant social contact rules in each tier. Indoor group activities and classes should not take place at tier 3

- Personal care and close contact services such as hairdressers and barbers, beauty salons, tattoo parlours, nail salons, spas and beauty services, massage parlours and tanning salons

- Public buildings, such as libraries, community centres and halls. They should not host events for private hire, such as birthday parties or most other social activities in tier 3 allotments, recycling and waste centres, public toilets, car parks

- Essential public services such as the NHS and medical services, courts, and jobcentre plus sites

- Places of worship - communal worship can now resume, subject to relevant social contact rules in each tier.

What about Christmas?

Travel restrictions between tiers will be lifted to provide a window for households to come together between the December 23 and December 27.

Up to three households can form an exclusive 'bubble' to meet at home during this period. Bubbles are fixed and must not be changed or extended further at any point.

Each Christmas bubble can meet at home, at a place of worship or an outdoor public place. But existing, more restrictive rules on hospitality and meeting in other venues will be maintained throughout this period.

And what about visiting care homes?

Visits to care homes CAN take place with arrangements such as substantial screens, visiting pods, and window visits.

Regular testing will be offered for up to two family members or friends per resident by Christmas, which — when combined with other infection-control measures such as PPE — will support indoor visits with physical contact.