The A40(M) was a former motorway in West London. For purely political reasons. In 2000, all roads within Greater London were transferred to a new body, "Transport for London". Unfortunately, whoever wrote the legislation made an error, and TfL have no power to be the authority in charge of motorways... It was something like 2.5 miles (4km) long, so it's fairly short, I guess. It's still an important route through west London, it just doesn't have blue signs any more.
The A41(M) is grandly titled "The Watford - Tring Motorway" in a set of 1970s motorway strip maps. It never got beyond being "The One Side of Tring - The Other Side of Tring Motorway", although it was meant to follow the line of what is now the upgraded A41 to the present M25, and then beyond to the original northern end of the M25 at J19a.
In addition, the A41(M) was then due to continue over the top of Hunton Bridge Roundabout, and then would have ended in the area of Berrygrove, or M1 junction 5 to most people!
It then got downgraded in 1987.
And it's absolutely nothing to do with the M41. Not at all. Not ever. No matter what you might read elsewhere - the two roads only have the number "41" and the fact that they are in South East England in common. And the A41(M) was never meant to go to Birmingham either - that's an urban myth based on utter speculation. There is no evidence of the motorway being extended north of Tring - and indeed it crashed into a roundabout at that end.
The A46(M) was a former motorway. It's at M1 J21 - the main access to Leicester from the M1. There isn't much to say about it except for it was a spur of the M1 to access Leicester and the A5460.
The A102(M) was former name for the Blackwall Tunnel. This was the southeastern section of Ringway 1.
Oddly, the Blackwall Tunnel Northern Approach was never designated as a motorway, only the Southern Approach. The Blackwall Tunnel itself was also never designated as a motorway, despite some 1970s maps telling you otherwise. Surprisingly, or not if you've been paying attention, it would have met the South Cross Route, which would have headed across to Battersea where it would have met the West Cross Route, or M41.
The A6144(M) was a spur of the M60 in Western Manchester. The original plan for the Spur involved a normal everyday dual carriageway motorway. It is mentioned in its own right in planning documents from the early 1970s, and as part of a larger scheme before that. In common with many projects of the time, it was canned in the mid 1970s. You can see just how early on it was planned - there was a junction number left free on the M63 for it.
However, the Spur refused to die.
It was resurrected on the cheap in the 1980s, and a single carriageway was laid down, with the possibility of later dualling.
