Actually the M was planned first  it was to be a guinea pig road which spawned the M later The M at Preston originally opened as dual  lane with soft shoulders which apart from an extra lane each way was exactly how the M was constructed The media arent a reliable source with roads history Archive material from planning offices however is For what its worth  construction of the M began first with the embankments for the Barton Bridge being placed in anticipation for the eventual StratfordEccles Bypass