There comes a point when it starts to feel a little pointless to rebut, once again, the charge that the Conservatives are going to privatise the National Health Service.

As one Tory strategist put it to me recently, the whole idea is so electorally toxic that it is straightforwardly impossible to imagine the Party doing it. No Conservative Prime Minister, let alone one who wants to be liked as much as Boris Johnson, wants a trade deal with the US more than they want to win the next election.

As is often mentioned, the Conservatives have presided over the NHS for the majority of its 70-year history. In fact, such is the Tory terror of being perceived as anti-NHS that they actually give themselves less room for manoeuvre on the issue than Labour.

After all, private involvement in the Health Service expanded more quickly under New Labour than under subsequent Conservative-led governments, and it was Andy Burnham, whilst Health Secretary, who oversaw the opening of the first privately-run NHS hospital.

So it isn’t particularly surprising that Jeremy Corbyn’s claim to have secret documents proving a Tory plot to sell the NHS have proven, upon closer inspection, to reveal nothing of the sort. The closest Labour have got to an actual attack line is a few comments from UK officials regarding patents and “NHS access to generic drugs” – the UK has shorter pharmaceutical patents than America, which allows the Health Service to start buying cheaper generic alternatives more quickly.

But as FullFact point out, this merely represents an acknowledgement that the area will be important to US negotiators rather than any sort of agreement with the American position. Moreover, these papers are from preliminary talks between officials, rather than inter-governmental negotiations, and predate Boris Johnson’s taking office as Prime Minister.

Given the thinness of the evidence, once can’t help but wonder whether this was a stunt the Opposition had been hoping to hold back until closer to polling day before Corbyn’s car-crash interview with Andrew Neil forced them to reach for whatever they could to change the headlines.

Of course, it could yet move the dial – there are doubtless plenty of voters quite prepared to believe that Johnson would sell the NHS to Donald Trump, although how many of those are swing voters is another question. Moreover the nuances of the debate might be lost on those not following it closely – Labour politicians are seldom keen to clarify in voters’ minds the difference between private provision of NHS services and US-style paid-for healthcare.

But by deploying this, the great Labour weapon of last resort, a full two weeks out from polling day, Corbyn has given both the Conservatives and their media allies much more space than he might have liked to mount a counter-offensive and pick the charges apart.