Yesterday I took a call from a senior member of London’s Jewish community. He is a longstanding supporter of Labour, a significant donor, and a champion of Keir Starmer and his efforts to reform his party. ‘He’s lost the community’, he told me. ‘All the work he’s done over the past few years. It’s been destroyed in eight weeks’.

On October 10 last year, three days after the appalling Hamas terrorist attack, Keir Starmer turned up at a Labour Friends of Israel reception at his party conference in Liverpool. With his shadow foreign secretary David Lammy at his side, he solemnly declared: ‘In this dark hour, Labour stands with Israel’. He added: ‘Labour stands firmly in support of Israel’s right to defend itself, rescue hostages and protect its citizens.’

Keir Starmer leaves 10 Downing Street today

It was all a lie. On Monday the Prime Minister signed off an arms embargo on Israel that will undermine its capacity to defend itself, rescue its hostages and protect its citizens.

There was no robust legal basis for the decision. As Mr Lammy, now Foreign Secretary, admitted to the House of Commons: ‘We have not, and could not, arbitrate on whether or not Israel has breached international humanitarian law.’

It was internally incoherent – systems to allow accurate aerial ground targeting were banned from export, but the aircraft doing the targeting were not. It immediately backfired diplomatically, as Israel condemned ‘this shameful decision’. And it produced an equally vigorous backlash from the Corbynite faction within Starmer’s parliamentary party, which condemned his failure to introduce a ban on all armaments.

But what provoked the anger of leading members of the Jewish community most was the timing of decision. ‘It beggars belief’, Chief Rabbi Ephraim Mirvis declared, ‘at a time when Israel is fighting a war for its very survival on seven fronts forced upon it on October 7, and at the very moment when six hostages murdered in cold blood by cruel terrorists were being buried by their families’.

Over the past couple of months the jury has been out on Starmer’s premiership. There have been some signs – such as his strong and decisive response to the riots – that he is comfortable and competent when it comes to the day-to-day demands of his new office. Equally, we have seen backbiting, infighting and confusion among his inner-circle on a scale that indicates he has not yet imposed his authority on his government.

But with Monday’s arms embargo decision we finally have something definitive to work with. And it’s this. You simply cannot trust a word the Prime Minister says.

The Jewish community, who were told unequivocally Keir Starmer would be an ally to their relations and friends while they were under barbaric attack. Britain’s pensioners, who were assured during the election they had nothing to fear, ‘and a lot to gain’ from a Labour government. ‘They are safe with us,’ he promised on July 1.

Then on July 29 he despatched his Chancellor Rachel Reeves to announce winter fuel support would be axed for 10 million over-65s. The nation’s hard-pressed tax payers who were told no fewer than 50 times that: ‘Labour will not raise taxes on working people’. And who are now being warned they face a £22billion bill for clearing up ‘the Tories’ mess’.

The Prime Minister has been embroiled in a ‘passes for glasses’ scandal prompting allegations of cronyism, which he had promised to crack down on before coming to power

Each of these groups have learnt the hard way. Keir Starmer will indeed stand with you – for just as long as it remains electorally expedient. And then when it isn’t, he will cast you aside.

To be fair to him, he has never been very good at masking this cynicism. From the moment he unveiled the ten Left-wing ‘Pledges’ that secured him the Labour leadership, his political principles have always been disposable.

And to be equally fair, this approach has served him well. In five years he has guided his party from the brink of oblivion back to power.

But he needs to be careful. Because now the British people are on to him.

They expect their politicians to play fast and loose with the truth. They still remember Boris Johnson’s shocked expression at Prime Minister’s Questions as he claimed he had just been informed parties had been taking place in Downing Street during lockdown. They are still searching in vain for the 50 new hospitals that were supposedly being built on the last government’s watch.

But the voters remember something else. They remember when Keir Starmer had just been cleared of breaking lockdown rules in Durham, and announced: ‘What you will always get from me is someone who believes honesty and integrity matter’. They recall his New Year speech, where he pledged ‘no more VIP fast lanes. No more kickbacks for colleagues. No more revolving doors between government and the companies they regulate. I will restore standards in public life with a total crackdown on cronyism’.

And they can see, again, that it was all a lie. Labour donors are being parachuted directly into the heart of government. Starmer pocketing nearly £20,000 in new suits and new glasses, then giving his sugar-daddy an access-all-areas pass to Downing Street. Cronyism at its finest.

But at least now we know. After two months the mist is finally lifting. And we can all begin to see what Keir Starmer is, and what he isn’t.

He seems a competent manager. He appears relatively calm, and steady under fire. He inclines towards pragmatism, rather than populism or radicalism.

But he deflects and dissembles and distorts just like all the rest of them. He will embrace an idea or a group or a faction for precisely as long as he deems it in his political interests. And then when it isn’t, he will ditch them without a second thought.

Starmer could still prove to be a good Prime Minister. With a little good fortune, and the continuing assistance of his Tory opponents, he could even end up a great Prime Minister.

But we now know for certain what he will not do. He will not restore faith in our politics. He will not end cronyism. He will not place honesty and integrity at the heart of his government.

Because Starmer is not the man he pretended to be. Or that his supporters told us all he would be. He is no knight in shining armour, cantering down Whitehall on a glistening white steed, the flaming sword of truth and justice locked in his steely grip. Instead he is just another middle-aged, north London lawyer, with vaguely progressive leanings who has fought his way up the political ladder, and is damned if he’ll let anyone drag him down it again.

So now the Jewish community, pensioners and working people have served their purpose. They are expendable. Keir Starmer needs new allies and coalitions – has a need to craft fresh narratives about ‘tough decisions’ and ‘hard choices’ and being ‘a candid friend’.

But he’ll be back eventually, trying to court those betrayed groups once more. When election day again hoves into view Keir Starmer will be there – with his pledges and his promises and his commitment to stand in stoic solidarity.

But at least then they will be forewarned and forearmed. Just as we all will be. Each of us of comfortable and sure in the knowledge we once again cannot trust a single word our Prime Minister says.