The Government will "rule nothing out" on the prospect of a new fourth tier of restrictions, Matt Hancock has said.
The fourth tier is thought to be viewed as a short-term option, which could be deployed instead of national circuit-breaker restrictions in order to get the spread of the virus back under control.
The Scottish Government has opted for a five-tier model in which Level 4 is closer to the full lockdown.
Why do we need a Tier 4?
In August, the Department for Education published a four-tier structure, in which all educational institutions - including primary schools and early years settings - would be shut. Existing Tier 3 measures include the closure of pubs and bars that do not serve food, topped up by shutting gyms, soft play centres and casinos.
Asked about it on October 26, the Health Secretary told BBC Breakfast: "We've always said all along that we take nothing off the table. Having said that, we have seen the rise in the number of cases has slowed a bit.
"The problem is it's still going up, and while it's still going up we've got to act to get it under control. We rule nothing out but at the moment the three-tier system is what we're working to and it's effective in slowing the growth of this virus but it hasn't brought this curve to a halt."
Government scientists including Prof Chris Whitty, the Chief Medical Officer, have warned that the "base line" Tier 3 restrictions were unlikely to be enough to bring down the R-rate alone.
Which areas might go into Tier 4?
The Liverpool mayor, Joe Anderson, has backed the idea of a possible fourth tier of coronavirus restrictions if Tier 3 measures do not go far enough to halt the spread of Covid-19.
Mr Anderson, whose brother Bill was one of 61 people to die with the virus in the city in one week, said he would support "tougher measures if necessary".
He told BBC Breakfast on Oct 27: "It has taken untold damage on people's wellbeing and a huge toll on families where people have died. If anything was required to bring it down faster I would do that.
"However, I want to make sure that we are giving tier three a chance to see if the measures have an impact."
He added he would review the results of the Tier 3 restrictions in 14 to 16 days' time.
Areas already in Tier 3 would be most likely to be moved up.
As of Oct 27, these are the areas of Liverpool and Merseyside (including Knowsley, The Wirral, St Helens, Sefton and Halton), Lancashire and Greater Manchester, South Yorkshire (including Sheffield, Doncaster, Barnsley and Rotherham) and Warrington.
Nottingham, Broxtowe, Gedling and Rushcliffe Council areas are set to move to Tier 3 Covid-19 restrictions on Thursday, October 29.
What would be Tier 4 restrictions?
The existing Tier 3 restrictions are as follows:
Pubs and bars must close, and can only remain open where they operate as if they were a restaurant - which means serving substantial meals, like a main lunchtime or evening meal. They may only serve alcohol as part of such a meal
Wedding receptions are not allowed
People must not meet anybody outside their household or support bubble in any indoor or outdoor setting, whether at home or in a public space. The “Rule of Six” applies in open public spaces like parks and beaches
People should try to avoid travelling outside the ‘very high’ area they are in, or entering a ‘very high’ area, other than for things like work, education, accessing youth services, to meet caring responsibilities or if they are in transit
People should avoid staying overnight in another part of the UK if they are resident in a ‘very high’ area, or avoid staying overnight in a ‘very high’ area if they are resident elsewhere
Extra tier three-plus or potential tier four restrictions could mean restaurants and non-essential shops are forced to close.
Under a distinct tier system created by the Department for Education, all educational institutions, including primary schools and early years settings, would be shut.
When will Tier 4 restrictions come in?
Matt Hancock ruled nothing in or out when he was asked about it this morning, but it is thought new restrictions could be introduced in some parts of the country as early as November.