Will the M3W need a front number plate?
The answer seems to depend on whether the law thinks it has a body that is car-like. If it looks like a car then it needs a front NP, if it doesn't look like a car then it
must not carry a front NP, unless it was made before 1st September 2001, in which case it
may have a front NP if it likes. This means that the pre-war original M3Ws, which once upon a time had to have a front NP under English law, have not needed one since 2001, but can carry on showing one if they wish.
I think the current law is The Road Vehicles (Display of Registration Marks) Regulations 2001. For the purposes of these regs the M3W is defined as a motor tricycle:
http://www.legislation.gov.uk/uksi/2001/561/regulation/2/madeSection 2 (1) says a motor tricycle means a vehicle having 3 wheels symmetrically arranged.
For a motor tricycle, section6 (5) of the regs says:
(5) In the case of a motor cycle or a motor tricycle which does not have a body of a type which is characteristic of the body of a four-wheeled vehicle—
(a)a registration plate must not be fixed on the front of a vehicle if it was first registered on or after 1st September 2001, .
(b)a plate need not be fixed on the front of the vehicle if it was first registered before 1st September 2001.
So, if the M3W looks like a car, these regs do not apply, but if it does not have a car-type body then the regs must apply.
In my view, the M3W does not have a car-type body because it has received (last Friday) type approval for the road without meeting the rules required for a car: it has exposed exhausts, a pedestrian-unfriendly exposed engine at the front and so on... The registering authorities must have assessed it as a vehicle which does not have a car-type body. Therefore, it seems to me that if we put front number plates on our new M3Ws we will be in breach of Section 6 (5) of the Road Vehicles (Display of Registration Marks) Regulations 2001.
Clear as mud?

Any other views out there?

Notlob