I have just added this to the map of places to fly your drone at Drone Scene:
Land owner permission requirements unknown.
Parked in the Layby opposite, used that to TOAL and over flew the field opposite.
No challenges from anyone that I encountered.
The originator declared that this location was not inside a Flight Restriction Zone at the time of being flown on 20/08/2021. It remains the responsibility of any pilot to check for any changes before flying at the same location.
Nice one!
Re: land owner requests—
Visited yesterday hoping to get some nice shots, but was disappointed to see signs saying “absolutely no drones allowed, police will be phoned and you will be prosecuted.” Probably would be within your rights to take off from the lay-by or the public access trail across the road but didn’t feel like fighting anyone.
Who owned the signs?
For trespass? 
Can’t get police to turn up, within a week, for burglary and attempted scamming of old ladies of £7k.
A year after the attempted scamming, the police called to ask me (as a witness, and interceptor of the scam attempt) for additional info.
When I asked if they’d made any progress on finding out who it was, they said they knew who the perpetrator was, that he was still in action, and still using the same mobile phone.
When I asked why he hadn’t been arrested, prosecuted and jailed … he quite honestly replied that they don’t have enough time for “such unimportant crimes”.
So - I reckon a landowner would need to hold you for a good 5 years before the police arrived for possibly flying a drone where you shouldn’t. But then he’d be arrested for unlawful imprisonment …but never prosecuted.
The signs are referenced in this foi request:
The signs were posted on the gate to access the field. Take from that what you will.
I would be quite interested to know what they would actually try to prosecute you under; the only thing I can figure is that since the viaduct is (used to be?) a rail line they might try to get you for the often quoted “flying within 50m of a rail line”.
That old chestnut.
That’s not actually a law.
These people eh? 
I think it would be ok to fly the other side of Borde Hill Lane in the field next to the Ouse pathway.
As you can see above, this sign has been noted, already.
Sign say not to fly … I suppose I can’t fly over the viaduct. But can I fly before it or near it to take photos ??
The sign is more photographed than the Viaduct
I’ve moved your post here @Tooting37 lots of good info.
In a nutshell I’d fly there
As a newbie to drone flying, I was quite put off by that sign. But after having a look at the Laws of flying drones near rail lines, I say I will be fine if you are flying more than 50m. 
Hi, did you fly your drone there in the end?
I pulled up on the other side of the road and flew. No restrictions and nothing legally preventing you from flying.
I have flown my drone just the other side next to the Ouse valley footpath. Around 250 meters from the Viaduct.
Also went flown my drone next to Ardingly Reservoir just off on a footpath leading off.
You may be able to see the Viaduct behind Ardingly reservoir center.
There are some no-flying drone signs around the path just next to the lake there as well.
I have done some investigation on this sign. I contact Mid Sussex District Council and Network Rail and both say they are not responsible for these signs. After looking the land registry it appears that the land adjacent to the Viaduct is owned by Balcombe Estate. I am waiting for a reply for them to confirm this.
If there are no bylaws attached to this land my thinking is that they could be break the law. The sign actually says ’ No operating a drone over this location’. I take this to mean no take off or landing here because it doesn’t state anything about flying a drone over this location. As long as you take off from the layby and do not fly within 50m of the viaduct there should be no problem.
Sounds like a good place for like minded people to meet. Obviously would have to car share as there is limited parking. Just a idea.
Just to clarify, in my last post I was referring to sub 250g drones only.
