Re-converting house to flats

[GrahamJ]

I own a detached house which was granted planning permission in the 60's to convert to 2 flats. Since then, house was converted to flats (I am told, but have only anecdotal evidence + some internal structural suggestive evidence) and then converted back to a single house, but not sure when.
If I want to convert it back to flats, can I use the original planning consent, or do I have to re-apply?

Cheers

G

[SMurray]

Good question! Looking forward to hearing an answer.

[pilman]

Official answer would be that you need to apply because a change of use from a single dwelling to two dwellings is development.

Real life answer is to consider whether the planning department would know that the conversion to flats has been abandoned.
If you now reinstate the building into two flats, as granted permission, will anyone be prepared to dispute that this change had been implemented in the 60's and had continued to be development that had the benefit of that original permission because the work had been started.

If you reconvert to two flats, after 4 years this will be immune from enforcement action and therefore lawful. If the planning department became aware of the development they could issue an enforcement notice any time withing a four year period, if they consider it worth doing so.
Your original planning permission may convince them that it is not worth doing so if the current local plan still allows such conversion if an application was to be made retrospectively.