If the last election was punctuated by the chant of "Oh Jer-e-my Cor- byn" at Labour rallies, this time its the roar of "Not For Sale, Not For Sale" about the NHS that’s getting Labour supporters fired up.
This has had the government scrambling to utter furious denials.
With the help of the independent fact checking organisation Full Fact we thought we’d look into this claim.
Is the NHS 'on the table' in a future trade deal?
If you listen to President Donald Trump himself you might be none the wiser.
On his state visit to the UK in June he caused a storm by suggesting: "When you are dealing with trade, everything is on the table, so the NHS or anything else, or a lot more than that."
True to form, more recently, he was doing his best to row back from that telling Nigel Farage: "It’s not for us to have to have anything to do with your health service.
"We’re just talking about trade."
So far, so not clear.
But there is little doubt that in one specific way US trade negotiators would like better access to the NHS - on the price the service pays US pharmaceutical companies for drugs.
Currently the NHS has strict value for money criteria which means that medicines are judged on whether they are affordable as well as effective.
The US government has repeatedly complained that America pays too much for medicines in part because European countries pay too little.
A Channel 4 Dispatches programme last month, now regularly quoted by the Labour leadership, claimed UK officials had discussed drugs pricing in the NHS with the US.
Of course the government can still deny that it would ever agree to a deal that allows US drugs companies to insist on higher drugs prices here, but that doesn’t mean the US won’t push for it.
Which leads us to Labour’s £500 million a week figure - does that stack up?
Full Fact has examined that specific figure and concludes that drug prices could possibly rise after a UK-US trade deal.
But the NHS paying £500 million more a week is based on an extreme scenario.
This is why: "The £500 million figure is a rough calculation by a group of academics of how much more the NHS would pay if UK drug prices rose to match those in the US – a scenario that expert body the Nuffield Trust has said is 'fairly extreme'."
In 2017, the UK paid roughly £360 per person, while people in the USA paid £940.
That’s around two-and-a-half times as much.
The NHS in England spent around £18 billion in total on drugs in 2018/19.
A 2.5x increase takes you to around £45 billion, or about £519 million more per week.
It’s not possible to say what effect a trade deal that isn’t done yet would have on medicines.
But the Nuffield Trust told Full Fact that other countries that have done trade deals with the US covering medicines haven’t seen price rises to that degree.
Australia’s price gap hasn’t changed at all.
They conclude that presenting this figure as if it’s certain is "unjustified and misleading".
Even more so because it would be politically disastrous for any party to concede to anything near such a figure.
Why do we will still hear it?
Remember the bus?
The disputed "£350 million a week to the NHS" claim worked because it got people talking about the issue.
There might only be a grain of truth in the £550 million, but if its sowing doubt on an issue that people really care about, Labour clearly feel it’s fertile ground.