The following guidance should be followed immediately; the law will be updated to reflect these new rules;
https://www.gov.uk/guidance/national-lockdown-stay-at-home
You must not leave, or be outside of your home except where necessary (see above guidance for further information on what you can and cannot do).
Landlords, you may leave home to fulfil legal obligations or to carry out activities related to buying, selling, letting or renting a residential property.