I have just added this to the map of places to fly your drone at Drone Scene:
Land owner permission requirements unknown.
Right on the shoreline off the Mawddach Trail, this is a good nature environment
The originator declared that this location was not inside a Flight Restriction Zone at the time of being flown on 15/09/2022. It remains the responsibility of any pilot to check for any changes before flying at the same location.
Does the Afon Mawddach SSSI allow drone flight in this area ?
I have no idea, hence the ‘land owner permission requirements unknown’ tag but the video was shot a while ago, I can find no reference to the site in DataSet Wales and I flew over the estuary on a coastal zone. Designation may have changed in the last year or so.
Actually if you use ‘Altitude Angel’ you can see that this is now a caution zone. The cover of the SSSI is quite extensive now
You can also use our own Dronescene that you used to log the location 
Only with an upgraded log in 
Whereas I can get all the layers on AA with a basic account
A pound a month to fund this amazing site and dronesene 