Years ago, at the premises of the family business, there was regularly trouble with break ins. The factory was next to the railway line, they'd run along that, jump onto the roof, and in through the skylights.
The works manager stuffed rolled up barbed wire into the chutes below the skylights, so the hoodlums would have to negotiate that if they broke through the glass windows.
The Police and the insurance company both told them to take these barriers down, that they were illegal, that any burglar harming him or herself on them would sue and
would be awarded compensation.
So, this is a person who has already trespassed on your roof, then caused criminal damage to your skylight, forced entry, broken and entered ... and it is illegal, now he is inside your property illegally, to block his way with something that may cause him some harm.
I genuinely do not understand this country sometimes.
And, reading the above... how long before a burglar successfully sues the owner of a dog which bites a burglar who has
already broken in and is now inside the house.