It was Harold Wilson who announced that a referendum on EEC membership would take place on Thursday 5 June 1975.
The Labour Government had apparently "renegotiated" the terms of membership. The Cabinet then voted 16 to 7 to accept this "new" deal and to recommend staying in.
Some 145 Labour MPs were still opposed though and a Special Party Conference also voted to pull out.
The referendum itself was the first in British history. So the concept was new. Yet there had been two recent General Elections -in February and October 1974. Fatigue had set in and the campaign, Sanderson (2012) says, "never really cuaht the imagination." Indeed it only really "spluttered into life around the middle of May."
Wilson himself kept a relatively low profile. The unlikely star of the show was none other than Edward Hath who "hammered away with an articulacy and passion that astonished his critics." At rallies around the country -I saw him speak at a packed Paisley town hall- he "cut an implausibly dashing figure" and appeared to revel in his new found or rediscovered popularity.
The "No" campaign" officially called the National Referendum Campaign- was, by contrast, a rather unhappy ship. It was an uneasy coalition of left and hard right (Benn ended up sharing a platform with Enoch Powell) and it lacked both cash and momentum.
In the event 67% voted YES in a 65% turnout. A few days after the poll Wilson demoted Benn from Industry to Energy. The left was now in retreat.