One of the famous lines in the Sherlock Holmes stories is about the dog that did not bark. Because it did not bark it enabled the great detective to solve the crime.
The dog that has so far refused to bark at the centre of the British election campaign is Brexit.
Silence about the B-word is hardly surprising. Rishi Sunak cannot boast of it as a triumph.
Boris Johnson once described Brexit as a “Titanic success”, and for once he might actually have spoken the truth. Brexit has helped sink the British economy, divided different parts of the union of the United Kingdom, and significantly diminished the UK in Europe and also as a partner with the United States.
When Washington wanted to call Europe, British diplomats used to suggest, they often went through the British telephone exchange. How dated that sentence reads now.
Sunak won’t confront the problems Brexit continues to cause - including the massive spike in (legal) migration from non-EU countries. Yet it is more difficult at first to understand why Keir Starmer does not make the biggest failure in British government policy in years part of his attack.
He has his reasons. Labour politicians told me Starmer would avoid reopening the Brexit wounds because that would distract from the more obvious battles over the economy, cost of living, the NHS, public services and all the other connected issues we all care about. Besides, Starmer does not want to be accused of not recognising the supposed “democratic Brexit vote”.
But the real reason Starmer does not pursue Brexit was summed up by Napoleon: never interrupt the enemy when he is making mistakes.
Rishi Sunak is the most cack-handed general imaginable, leading the political equivalent of the Charge of the Light Brigade.
But the B-word question remains. It was left to Stephen Flynn of the SNP to bark about Brexit in the BBC TV debate, and he did so for obvious reasons. Scotland, like Northern Ireland voted to remain.
Whatever the troubles of the SNP (and they are considerable), even Scottish unionists have expressed to me a real sense of grievance that the 2014 Scottish independence referendum was fought by David Cameron and others partly on the threat that the only way for Scotland to stay in the EU was to stay within the UK.
The SNP are widely predicted to lose a lot of seats to Labour in this election, but the Conservatives are an endangered species in Scotland. The have declined since the 1950s with only the estimable Ruth Davidson managed to reinvigorate Scots Tories for a while. Now Scottish Conservatives are desperately beleaguered.
When I was writing my most recent book, two well known Scottish Tories told me separately that the “only way” to keep Scotland in the union of the UK is to have a Labour government. And - as some unionists also predict - Northern Ireland may indeed be edging closer and closer towards the exit door.
That brings us back to Brexit. The Good Friday Agreement plus the UK and the Irish Republic being together within the EU meant that we could argue about the border issue if so inclined, but it was barely an issue at all to have a border on a map, with little significance in our our day-to-day lives.
Now, however, Boris Johnson’s Brexit failure cannot be ignored in Northern Ireland, Scotland and across the UK.
If Keir Starmer becomes prime minister he will not want to be the leader who “lost” any part of the union. That means he will have to confront the dog that has not barked - and it will bark soon.
For now Starmer can get away with merely saying that under Labour the UK will have closer and better relations with the European Union. He can say that the threat to Ukraine reminds us that peace, prosperity, the EU and Nato are all in different ways linked. But he also has to decide what precisely he means about better relations with the EU.
Brexit has failed. It has to be rethought. The next British government will have to figure out how to end the self-harm
Meanwhile the diminishing number of Brexit enthusiasts are beginning to look as ridiculous as old time Marxists arguing that communism would be great if only we had done it “right”.
On social media last week I was challenged by a dyed-in-the wool Brexiter. He claimed that Brexit would have been a success if it had been done “full and proper”.
Yeah, right. The dog has not yet barked. But it will.
Brexit has failed. It has to be rethought. The next British government will have to figure out how to end the self-harm.