After Michael Heseltine's intervention at the weekend, today it's the turn of the europhiles' other big beast, Ken Clarke, to offer his two penn'orth on the Europe debate. In an interview  with the FT, the former Justice Secretary, who now attends cabinet as a minister without portfolio, warns that David Cameron's plan to hold a referendum on a "new EU settlement" for Britain could unintentionally lead to withdrawal. He notes:
All referenda are a bit of a gamble. I don’t think we can take a Yes vote for granted.
I think one of the problems is, because so much of the media is overwhelmingly eurosceptic, no one has really campaigned very vigorously for the case for British leadership in the European Union for probably a decade or more.
The problem for Cameron is that the gap between what Tory MPs want from a renegotiation (see the list of demands  issued by the Fresh Start group today) and what he can deliver is so great that he has set himself up for failure. As a result, he will find it harder to persuade his party and the public that Britain should remain in the EU when a referendum is held.
Elsewhere in the interview, Clarke, who has warned Cameron against seeking to use the eurozone crisis to repatriate powers from Brussels, bluntly compares those who support withdrawal to the "hangers and floggers" who demanded a referendum on capital punishment in the 1970s. "If you realise you’re doomed in parliament you demand a referendum – that’s what the hangers and floggers used to do," he says.
One issue that Clarke's fusillades against euroscepticism raise is whether collective ministerial responsibility applies to him. His plan to share a platform  with Peter Mandelson to argue for full British engagement with the EU suggests not. In response, we can expect eurosceptics to ask whether those ministers who privately favour withdrawal should also be free to put their case.
As I noted  earlier this week, the last time Britain held a referendum on the EU in 1975, Harold Wilson took the unusual step of suspending collective cabinet responsibility (as Cameron has over the boundary changes bil l) in order to allow his ministers to support either side in the campaign. Seven Labour cabinet ministers - Benn, Barbara Castle, Michael Foot, William Ross, Peter Shore John Silkin, Eric Varley - went on to unsuccessfully argue for withdrawal from the EEC (the vote was 67-33 in favour of membership). In this week's Spectator, James Forsyth reported that  there are "at least nine Cabinet members" who would be inclined to vote "out" in a referendum if Cameron only proves able to secure minor concessions such as the exemption of the NHS from the Working Time Directive
We're a long way off from a referendum but expect Cameron to be asked as early as Friday whether he would allow Conservative cabinet ministers to campaign for exit.