M1, M10 and M45
As mentioned earlier, the commonly held view that the M1 was the first motorway is false. It wasn't even second (as the M4 Chiswick Flyover opened in September 1959), but equal third, opening on the same day (2 November 1959) as the M10 and M45 - which as they were all part of the same project isn't all that surprising...
So now you've got that our of your system, tell us the story!
The first serious work by the Ministry on the London - Birmingham motorway took place in October 1937. This was simply an investigation into just how practical such a proposal was, and took the 1923 Northern and Western Motorway as its starting point, though it was considered whether starting the motorway on the A4 rather than Uxbridge would have been a good idea. There is, however, a small line at the end of the investigation:
If further information as to the practicability of a route is required, it is suggested that a line capable of extension east and northwest of Birmingham might be explored, as this would give a route more comparable with Trunk Route No.11 (A.5 and A.45)
Following this investigation, further work was carried out in February 1938. Irritatingly, the file in the National Archives (MT39/145, if you really want to know...) is incomplete, and so there is information missing. However, it appears that the route had been altered, and incorporated a more easterly route (somewhere between the 1923 and present routes) as well as considering how best to connect up to the route from Stafford northwards into Lancashire. The section in the West Midlands was to pass through Cannock Chase and head northeast of the conurbation, pretty much as shown here, with the addition of a possible spur from the route near Lynn, east of Brownhills, Staffordshire to West Bromwich. It also talks of a possible link from the motorway to the Blackwall Tunnel via the Lea Valley, and the following fascinating snippet:
I am also of opinion that the value of a motorway from London to the Midlands and the North West would be enhanced if access could be gained by it to Brighton as a distributing point along the South Coast. I therefore suggest a reconnaissance from the neighbourhood of Uxbridge, utilizing if necessary the route of the proposed South Orbital Road [now M25] and connecting up with and running alongside the new Trunk Route to Brighton [now M23/A23].
Not only that, but in the same report the North Orbital Road (A414, then Ringway 4) is recommended as well, along with double-decked viaducts and tunnels "where necessary". Rather disappointly, World War II then gets in the way of all this over-excitement, and upon the resumption of the project, things had been rather scaled back.
You might think that, but I couldn't possibly comment.
Work continued at a slower pace, until the Ministry announced the "South of Luton - Watford Gap - Dunchurch Special Road", which is the M1 between J10 and J18 and the M45, and the "Watford and south of St Albans - Redbourne - Kidney Wood Special Road", with this referring to M1 section between J10 and the "Aldenham Temporary Terminal" (near J5), as well as the M10 in 1956.
Work started on the M1, M10 and M45 on 24 March 1958, and the route was opened by Ernest Marples, the Minister of Transport in November 1959.
There is one "first" the M1 can lay claim to - it was the first motorway to be constructed as three lanes in each direction, though the National Archives tells us that it was a relatively last-minute decision...