It was 2 September 1939, a turning point in Britain’s history and its relations with continental Europe. Nazi troops were advancing through Poland, and prime minister Neville Chamberlain was making a somewhat vacillating statement in the House of Commons, which appeared to be giving himself wriggle room to dodge his commitment to the Poles.

Standing in for the opposition leader, Labour’s Arthur Greenwood rose to reply when he was interrupted by an appeal from halfway up the government benches. It was from the veteran Tory Leo Amery, who shouted: “Speak for England, Arthur!”

The phrase virtually guaranteed that Chamberlain did, after all, stand by his Polish commitment, and Amery played the key role seven months later in Chamberlain’s downfall.

It was one of those short sentences that carried within it a wealth of meanings that are not immediately obvious. The word “England” does not imply something parochial, but an admonition to speak from the best of us and the best of our history and for all of us.

Amery was the crustiest of imperialist Tories, yet he recognised that we had made commitments of honour to continental Europe, based both on morality and self-interest, which must be kept.

I thought of that exchange as the two main political parties which have dominated post-war life in the UK accelerated their collapse. You can interpret the referendum result in terms of either or both of them unravelling.

All the assumptions of that postwar world have been flung away. We now need someone, in that different sense, to speak for England – and beyond the current, very obvious divisions.

I believe that we have to take the referendum result seriously. We can’t just finesse it or constitutionalise it away. We also need to shape a narrative that interprets it in the most liberal way we can. In fact, history may belong to whoever can do that most convincingly.

Don’t let the only people speaking for leave voters, and interpreting their votes, be Nigel Farage and Marine Le Pen

Now I have my own biases, as a Lib Dem. But, say what you like about my own party, it is one political force that may be united enough to do that. Yet – perhaps for understandable reasons – it spent the first few days of Brexit claiming to speak only for the 48% who voted to remain.

I’m not of course advocating that the Lib Dems should abandon the cause, or to back off their fundamental internationalism. But the nation looks to any political force now capable of uniting them, and that means treating the other side with enough respect to lead them beyond the current impasse.

So this article is rather a public plea to one man. Tim Farron. Farron, history demands that you step into the breach and speak for England – in the sense that Amery meant it – and not just on behalf of the losing side either, but the winning one too.

The Lib Dems campaigned almost wholeheartedly for remain – the one political force that stayed united during the brutal referendum. But that doesn’t put the other side, now rudderless, outside meaningful dialogue. So this is what Farron should do.

Take this opportunity to articulate the liberal roots of at least part of the revolt against the EU (see the interviews with Brexit voters in the Guardian) – the rage at the banks, the commitment to local democracy and self-determination. It is no coincidence that former Liberal heartlands voted overwhelmingly to leave (Cornwall, Burnley, Torbay, Pendle, Isle of Wight). Because sometimes, for liberal-minded people, localism trumps Napoleonic international structures, and that doesn’t make them in any sense racist.

But don’t let the only people who are speaking for them, and interpreting their votes, be Nigel Farage and Marine Le Pen.

I know Farron is in Brussels today, speaking to liberal leaders from across Europe, which gives him the opportunity to speak beyond and above national interests.

He needs to look ahead to a new political division, when the great divide emerging is between nationalists and liberals, and where the division will not be 48:52. It is too early for coherent plans, but not too early to speak for the nation as a whole and at its best. For its fundamental tolerance, including on the Brexit side. For its outward-looking focus and its moral commitment to Europe, even from outside the EU – and, if necessary, our commitment to work for a reformed, flexible EU, even from outside it.

Because what we need now is a clear voice, not from one side or the other, but from the leader of a united party – who understands what the nation is, fundamentally, and says so, clearly and courageously.

Get it wrong, and liberalism will go down the same plughole as everything else. Get it right, provide the real liberal narrative of the Brexit protest, and we could just build a new nation.