Brake pipe falls of after mot

He did a couple of brake pipes, some work on suspension and welding chassis, the brake pipe in question was rear offside on an isuzu pickup, should be secured to axle, it was not, even so I think it was incorrectly flared,
Mechanic had car for 8 weeks, when questioned he blamed me for taking the car before he had performed final check after it had been to mot tester! Don't get that, surley if it's got mot should be safe to drive, also if it's not secured, this should have been picked up at test, in my opinion, would like professional opinion though before I start complaining to authorities, this is just the tip of iceberg with this guy, he has been refusing to invoice but demanding cash by threat and also assaulted me, police have warned him about that, now he's sending sky high bills not factoring in £900 he has already received! I could go on, but I just want some advice on this mot situation

Sound more like you need to involve Trading Standards in my opinion.

I thought that might be the case. Thanks for the confirmation.

Very hard to prove after MOT.
Always to remember that all ok at time of the test so very hard to prove otherwise unless severe corrosion.
Dvsa will explain this if you appeal the MOT.
Some people think they don't need even lift bonnet just because it's passed it's your responsibility to make sure vehicle is safe.
Thanks