He made the announcement in the daily briefing from 10 Downing Street.
This is what the new rules will mean:
- Who is covered by the new arrangements?
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Adults living alone or single parents living with children under the age of 18.
- What will they be able to do that they could not before?
They can form a bubble with one other household which means they will effectively be treated as a single household for the purpose of the lockdown rules.
That means they can visit each other indoors in their homes - staying overnight if they wish - and they will not have to observe the two-metre social-distancing rule.
- Who might benefit?
Elderly people living alone could form a bubble with the household of an adult son or daughter enabling them to visit and even hug their grandchildren for the first time since lockdown.
Single parents could pair up with their own parents allowing them to share childcare duties and reuniting grandparents and grandchildren.
Couples who do not live together will be able to visit and to stay with each other.
- What about households where both grandparents are still living - can they now visit their children and grandchildren?
At this stage only if their son or daughter is the only adult in the other household in the bubble.
Downing Street has acknowledged not everyone will benefit from the change although officials have hinted a further loosening of the rules if the coronavirus outbreak continues to decline.
- Can households form more than one bubble?
No. The arrangement must be exclusive with no switching of bubble partners.
- Will people have to formally register these bubble arrangements?
No, it will be taken on trust. No 10 says the public has shown "great responsibility" in following the social distancing rules so far.
- Is there any limit on the distance between households in a bubble?
Again no, although officials are suggesting people should try to "stay local" where possible.
- What about vulnerable people who are shielding due to their age or health problems?
At the moment, officials say it is too soon for them to be able to join support bubbles.
- What about parents who are separated but who currently share childcare with the children moving between the two households?
That will continue. If the parents are the only adult in the household they can form a bubble with another household - meaning the children could potentially be in two bubbles, one for each parent.
- What happens if someone in a bubble develops coronavirus symptoms?
All members of both households in the bubble must self-isolate for 14 days.