The question really is what the primary purpose of this traffic is at this point. It surely can't all be people driving to the Peak District to unnecessarily walk their dogs. I don't know.
There are 1.5million of us working for the NHS alone. Anecdotally, a lot of colleagues have started driving to work, as our new shift patterns make it a little challenging to guarantee being able to get home for many.
Extrapolating that to the many other frankly incredible people working to keep Public transport going, waste and energy management, water services, the police, fire departments...
I suspect there may be a logical reason for the uptick.
Again- anecdotally- the roads around the outside of Regent's were pretty full of parked cars, and the park itself was pretty hectic.
Most cyclists were trying to keep a distance, but some were still riding in bunches.
Extrapolating this- people are cunts.