Cheeky sods

[Al1963]

My elderly mother (78) recently widowed, was asked by a friend if they could store a sofa in her now newly empty garage.
She agreed and friend turned up to store said sofa with her daughter and daughter's boyfriend. Seeing a mostly empty garage the daughter's boyfriend took it upon himself to tell his father (I have no idea who these people are) of the location, and he has now dumped a variety of crap (mattress, furniture, motorbike) in there without permission.
Am I within my rights to remove all this stuff and dump it? Mum has asked this "friend" to get her acquaintance to remove it all by the weekend.
AIBU to think this is out of order and what do I do if they don't remove it?

Definitely get a camera OP trained on garage door and front door, preferably the sort that your DM can see anyone there from within the house.

Get the friend to sort this out giving just a short time period, and tell them if it has not gone you will be having a garage sale or put it on Freecycle. Why should you do the work for them by moving it for them or taking it to the tip?

YANBU, what cheeky twats.

Get it in writing that they have to remove the property illegally stored by x date, after which you will involve the authorities of a case of illegal flytipping.

I'd be telling them they've got 12 hours to get it out of there or a lock goes on and I start selling it all.

How long did it take them to move their shit in the garage? I’d give them the same length of time to get rid of it all. I don’t blame you for being angry. How fucking dare they?

If you don't want to issue ultimatums (and I'd be swearing at them by now) just tell them that the roof is leaking and they need to collect their stuff now.
Then I agree with everyone else get a ring doorbell.

I would create a gumtree ad saying free to anyone who can collect and send them the ad saying this goes live in 6 hours.

They removed it all this morning. Garage is now locked. Phew!

Well done OP. Now going forward your mum has reason to say no to anyone else who should ask, a past experience so best not to.

@Al1963

They removed it all this morning. Garage is now locked. Phew!

Did they give a reason as to why they thought it was okay to dump their crap at your mums? Did your mum's friend make them come back for it or did you speak to them yourself? I'm so glad this is all sorted but I must admit, I am very curious as to what the hell happened to make them think it was okay.

This was so very cheeky of her friend's daughter's boyfriend and his family. Totally unacceptable behaviour at any time but especially now when your Mum is more vulnerable .
Good to hear they removed everything this morning and garage is locked but I would seriously consider some security camera/system.
It would give both yourself and your Mum at bit more peace of mind.

@Al1963

They removed it all this morning. Garage is now locked. Phew!

It wasn't locked before? Anyone could just wander in?

I have no idea why they felt it appropriate to store more stuff in the garage. However they have removed it now. Yes my Mum's garage was left unlocked, she lives in a remote area where nobody would randomly find it and think they could store stuff.