Not legal: “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. A vehicle might still pass the MoT visible smoke emissions test, which is primarily intended to identify vehicles that are in a very poor state of repair, whilst emitting illegal and harmful levels of fine exhaust particulate.” See: www.gov.uk/government/publications/diesel-particul...e

Because removal of a DPF is already illegal, VOSA enforcement could happen overnight without warning, though I doubt that it will. Happily, there is a new service that can clean DPFs, giving them greatly extended lives at: www.ceramax.com.