The prime minister’s chief aide was also spotted taking a walk at another town 30 miles away during his stay, it is claimed.
However, Downing Street refused to answer the allegations in detail and described them as a “stream of false allegations”.
Here is a timeline of the events in question:
23 March: The UK is placed into lockdown with strict limitations on travel. Government guidelines state: ”You should not be visiting family members who do not live in your home.”
27 March: Downing Street announces that Boris Johnson and health secretary Matt Hancock have tested positive for coronavirus. Dominic Cummings is photographed running from No 10.
30 March: The government confirms Mr Cummings is self-isolating at home with coronavirus symptoms.
31 March: Durham Constabulary is told Dominic Cummings has travelled from London to Durham and is staying in the city.
1 April: A police officer speaks to Mr Cummings’ father by telephone. Mr Cummings’ father confirms his son travelled with his family from London and is self-isolating at the property.
5 April: A neighbour spots Dominic Cummings outside his parents’ property in Durham. The Guardian newspaper approaches Downing Street about the story and is told “no comment”. Boris Johnson is admitted to hospital after developing breathing difficulties.
12 April: Witness Robin Lees, a 70-year-old retired teacher, reportedly spots Mr Cummings in Barnard Castle, 30 miles from Durham. Boris Johnson is discharged from hospital.
14 April: Dominic Cummings is photographed returning to work in Downing Street after his self-isolation comes to an end.
19 April: Dominic Cummings is reportedly seen walking near his parents’ home in Houghall Woods by another witness who later tells the Observer and Sunday Mirror that the adviser commented: “Aren’t the bluebells lovely?”
25 April: An article by Mr Cummings’ wife Mary Wakefield about the family’s experience of self-isolation is published in the Spectator magazine. It does not mention the stay in Durham.