Interesting story on diesel particulate filter removal by the BBC, BBC News - Stoke-on-Trent garages 'illegally remove car emissions filters'
Yet removing them isn't illegal, it's only illegal if the vehicle is used on the roads.
It is an offence under the Road vehicles (Construction and Use) Regulations (Regulation 61a(3)) to use a vehicle which has been modified in such a way that it no longer complies with the air pollutant emissions standards it was designed to meet. Removal of a DPF will almost invariably contravene these requirements, making the vehicle illegal for road use. The potential penalties for failing to comply with Regulation 61a are fines of up to £1,000 for a car or £2,500 for a light goods vehicle.
And interestingly, to quote. "A Department of Transport statement said all MOT garages would be notified on 26 October they risk losing the authorisation to perform MoT tests if they offer to remove the filters."