Its first section opened in 1973, and the rest was all built, but the A41(M) doesn't exist. It was canned in favour of orbital roadbuilding, and later resurrected in a more modest form.
In days gone by, new roads were often celebrated with a grand opening ceremony and the issue of a commemorative booklet heralding the exciting new highway. You'll find some of them here, complete with a glimpse of all that empty tarmac and a healthy dose of modernist optimism.