so if you remove the cat you dont pass the MOT?
therefore its not legal for you to drive your car
so how comes so many people do it?
im confused
Not quite. There's no requirement whatsoever for a car in the UK to be fitted with a catalytic converter. However, it's unlikely that it'll pass the UK MoT emissions test without it being in place and working correctly; also, the supporting infrastructure (lambda sensors, MAF and everything else) will need to work correctly for this to be the case.
WE need to be careful here. It's not necessarily illegal, but is probably unlawful. Further, it's possible to find yourself on the wrong side of the law for doing something unlawful. It doesn't have to be illegal for you to be challenged.
If you can get your car through the MoT test without a CAT then you are at liberty to drive it around without one (a cat, not a valid MoT test certificate). And if it passes the Mot without the cat then the roadside emissions lot will never stop you on account of visible emissions because if there were any (visible emissions) the MoT test would have been aborted immediately.
You have to be careful because removing the cat constitutes a vehicle modification. And your insurers might see fit to void your policy if you had occasion to make a claim upon it if you had not disclosed such a modification. Again this does not mean that you are using your car illegally, although you are possibly using it unlawfully.
It's a dark grey area. But if your insurer decided to void your policy on account of undisclosed Modifications in the event of a RTA then you will be found guilty of the offence (illegal this time) of driving without adequate insurance should your insurer elect to decline a claim.
THe best thing you can do is discuss your plans with your insurer and gain agreement IN WRITING that your policy is valid. You need to get it written into the policy schedule and make certain the the certificate of motor insurance refers to that that schedule specific to your policy.
it's strange that we need to go this far with a midified car because insurers will happily pay out for an accident caused by a druken policy holder.
That's BRitish law for you. Unpredicatable at best. Unreliable at worst.