From what I’ve heard from Camden Council officers, the following article and CNJ reports, I suspect it would be highly unlikely for short term lets: https://www.camden.gov.uk/ccm/content/environment/planning-and-built-environment/two/planning-applications/before-you-apply/residential-and-business-projects/short-term-lettings/
The takeaways seem to be the amount of time you intend to let out your property for:
Less than 90 days in any one go: “You will need to apply for full planning permission to convert a flat or house into a short term/ holiday let if you intend to let the property for periods of less than 90 days for more than a total of 90 days in any one calendar year… Current planning policy in the Council’s Local Development Framework is to resist development that changes permanent housing to short stay accommodation/holiday lets”
With the caveat: “Permission is not required… if you let a room within your property whilst you are still living there.”
More than 90 days, just in case you can stretch to that: It is very possible you you must notify Camden Council otherwise you will have breached your lease with whatever risk that entails. Camden Leaseholder Services do have procedures in place for official sublets of more than 90 90 days.
p.s. Anthony make same useful points about subletting over here: https://www.leaseholdersforum.org.uk/discussion-post/subletting-my-flat-have-you-encountered-any-problems/
Sorry for the bad news!