Ideas for solutions to help much appreciated. (Elderly DM and neighbour with dementia).

@MerrilyMoving Has the neighbour issue improved or worsened?

Glad you have now installed a camera, and have advised from social services.
I do think your mom needs to take additional steps to secure her gate . This doesn’t mean she’s locked in . I have a simple chain on my gate to stop the dogs from opening it .

I would advise her to keep a log of times, dates etc.

It also might be worth logging with the police on the non emergency number (101?) each time.

She is being harassed and it's not on (no matter the reason).
You could could try adult social services.
Also mp's can some times help with things like this(some of them have high up connections /can get things done in some places).
Unfortunately I suspect things will probably get worse before they get better which is why she should log everything. If his family are reluctant to get involved it could be a long slog /high threshold before ss step in/action is taken. I hope not but sadly expect you will need to keep reporting and keep escalating things with police/ss etc :(
I wish you well, it's a sad situation all round :(

Unfortunately all ours are old antique ones so I can’t advise where to buy one in person, but I’ve just googled and there’s loads online.
A spring clip one, like a horses lead rope might work too if you cant find the T bar type.

@MerrilyMoving When you register your elderly, vulnerable loved one with SS, they keep a register (at least my County does). It means if there's an incident (fire / police / ambulance), these services are aware. Also, they will send an OT to see if there is anything they can offer to help with independence - half steps, rails, shower grab rails etc.

The PSR will ensure that they are notified in the case of a power cut / water being cut off and so on, and the utilities prioritise their reconnection where possible. It means that they don't need to worry about contacting the utility company if something goes wrong, they will be notified.

Also if your mother has a digital VoIP telephone, she can get a UPS so that in the event of a power failure, she is not left without communications.

There's lots of help out there, but tracking it down is tortuous.

With regard to the neighbour, are all the houses similar? If your mother's house looks like his, he may well think that it's his house, hence the trying to get into it. He could be coming out of his house, seeing the house opposite, recognising it as looking like his and 'going home'.

My father had dementia. They really do live in a completely different world. The easiest way of dealing with resultant behaviour, is to put yourself in their world and try and see things how they do.

It's a sad situation all round.

Securing the gate without locking is a good idea OP. Have you ever come across a Cow Chain? Not sure thats its proper name, but basically a chain with a bigger circle and a T shape on the ends that you put through the circle to secure. We have them on our horse paddocks and it’s amazing how many people that haven’t come across them can’t work out how to open them! They’d definitely outsmart him if he's not thinking well and lost fine motor skills while being easy to use if you know how. Such a shame his family won't engage because they’d probably have better ideas about what would put him off.

No i wouldn’t help here but worth doing nonetheless. DM is over 90 and doesn’t consider herself old or vulnerable!

are there any other neighbours who he is bothering or could keep an eye on her? Is he under a delusion that she is in his home somehow? Might be worth speaking to a dementia charity for their take on the situation and advice.

PSR is a database of those who may need more support if there is a power, communication or water outage. To deliver bottled water for example. It covers not only the elderly and households with children under 5 but those with health conditions, disabilities or otherwise vulnerable . The utility companies will have an online page to notify them.

Please don't do this. The man has dementia. Do any of you writing these kind of responses actually have experience with dementia and the effects of cognitive decline ?

And the OP's mother is an elderly lady, she needs safeguarding, not placing in a potentially harmful situation.

@MerrilyMoving Adult Social Services for both of them. The male neighbour needs a proper care assessment as he is wandering. This is hugely dangerous for him. His family should be ashamed of themselves blaming your mother. It's a total failure of care on their part.

Your mother is vulnerable and needs protection, not just from him, but SS do need to be aware in case of emergency. Is she also on the priority services register for her utilities? I would also advise you call AgeUK for help/advice.

My grandma was a nuisance to her neighbours when she had dementia. It was awful for everyone. But we always talked to them and listened and did our best to help them. We didn't ever make it their problem. I'm sorry your mum's neighbours aren't listening and acknowledging the problem. That's the least they could do.

I'm sorry this is happening to your mum.

I think you said you hadn’t seen this happen? Could you get ring camera/CCTV/whatever it’s called, but access the live footage from your phone? Then you have either a recording to show police or social services, or you can call the police yourself. When you dial 999 (because it will be an emergency) you just have to say ‘I’m calling from London but the emergency is in Leeds’ or whatever.

Or the other thing lots of dementia wards do is do a code for the door, printed on a piece of paper inside a butterfly (no idea why it's always a butterfly) next to the door. So everyone who doesn't have dementia knows what the code is (so can deliver the post etc) while those with dementia can't get through.

Well the padlock on side gate is a no-brainer - sort that straight away. But then it's a call to adult social care, definitely.

Could you put two handles on the gate , one that pushes down and one that pushes up . Similar to nursery/ reception class doors as he might not figure on how to work them .

I wonder if another idea would be to make a safeguarding report for your own mother. She's 85, and therefore very likely to be classed as a vulnerable adult, and being intimidated by a neighbour.

Until I saw your diagram, I hadn't appreciated re the gate that she would then have no way to receive post etc, so I do certainly see why she isn't a fan of that idea.

I like the bullhorn idea !

Could you encourage her to shout ‘Go Away, John!’, with her hand up like a stop sign? Or carry a bullhorn to blast at him?

And is there another neighbour she could ask for support? If I was aware of the situation, I’d drop everything to dash out and help when I heard the horn or saw him coming.