When Boris Johnson introduced the UK lockdown he gave “a very simple instruction – you must stay at home”.

But it has now emerged that his chief adviser, Dominic Cummings, allegedly broke the rules just days later by travelling 260 miles from his London home to his family home in Durham.

The rules, announced in a speech the Prime Minister made to the nation on March 23, stated that people would only be allowed to leave the house for limited purposes.

These were shopping for basics, one form of exercise a day, travelling to and from work, but only where absolutely necessary, and medical needs.

Reinforcing the message, Mr Johnson said people should not meet family members who do not live with them.

The rule on meeting family was unequivocal.

It stated: “You should not be visiting family members who do not live in your home.

“You should keep in touch with them using phone or video calls.”

Only in exceptional circumstances were people allowed to attend relatives’ addresses; for example, to drop off food or medicine to their door.

Even now the lockdown rules have been relaxed slightly, visiting friends or family in their own homes is still off limits.

The current guidance states: “As with before, you cannot visit friends and family in their homes.”

The Government guidance also said: “We are advising those who are at increased risk of severe illness from coronavirus (Covid-19) to be particularly stringent in following social distancing measures.

“This group includes those who are aged 70 or older (regardless of medical conditions).”

It added: “If you are showing coronavirus symptoms, or if you or any of your household are self-isolating, you should stay at home – this is critical to staying safe and saving lives.”

Even before the lockdown, Mr Johnson set out a stark warning to the nation, saying on March 16 that “now is the time for everyone to stop non-essential contact and to stop all non-essential travel”.

Downing Street previously confirmed that Mr Cummings had started displaying coronavirus symptoms “over the weekend” of March 28 and 29.

He is alleged to have been present at his family home when police from Durham Constabulary turned up on March 31, following a call from someone reporting they had seen him in the area.

Durham Police confirmed officers had spoken to the owners of an address in the city after reports that a person had travelled there from London.

Officers “explained to the family the arrangements around self-isolation guidelines and reiterated the appropriate advice around essential travel”, the force said.