One of the unanswered questions about the Brexit talks is whether Theresa May is deluded, dishonest or both.

Exactly one year ago, the prime minister stood in Lancaster House and gave a speech setting out her Brexit plan. Following an embarrassing series of flip-flops, it now reads like a long list of broken promises and empty threats.

May said she would provide “certainty” to business. But the lack of clarity over our future deal with the EU – which the cabinet didn’t even start debating until just before Christmas – has led to a virtual freeze in investment.

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The prime minister said she wanted the greatest possible access to the single market without being a member of it, her version of Boris Johnson’s cake-and-eat-it approach. She also knew this was going to be tricky to get. That is why she threatened to turn the UK into a Singapore-style tax haven while hinting that we would abandon cooperation with the EU on fighting terrorism if she didn’t get her way.

But threatening the EU wasn’t smart, given that we need it more than it needs us. So it didn’t take long for the prime minister to eat her words.

The same goes for her “no deal … is better than a bad deal” mantra, which was given prime billing in the Lancaster House speech, and her promise that “the days of Britain making vast contributions to the European Union every year will end”. As it is, May has ended up promising £39bn to the EU to settle our past bills, and abandoned her “no-deal” bravado.

Some of the prime minister’s assurances now read as bad jokes.

Take her promise to “strengthen the precious union between the four nations of the United Kingdom”. Many Scots are furious at her decision to rip us out of the single market. Meanwhile, if she sticks to her promise to pull us out of the EU’s customs union, she won’t be able to avoid either a land border in Ireland (which would set back the peace process in Northern Ireland) or a sea border between Ireland and Great Britain (which would infuriate her allies, the DUP).

Our former EU ambassador warned the government this would lead to us getting ‘screwed’ – and it has

Or look at May’s pledge to “bring an end to the jurisdiction of the European court of justice”. By the summer, the government was only saying it wanted to stop the court’s “direct” jurisdiction. What’s more, we’ll have to follow all the EU’s rules during the transition period the prime minister is now desperate to agree so the economy doesn’t fall off a cliff next March. So much for “taking back control of our laws”.

May also said she would protect workers’ rights. But just before Christmas, hardline pro-Brexit ministers started campaigning to axe the working time directive, which stops people being forced to work excess hours and guarantees paid holidays.

Yet another of the prime minister’s pledges – to cut a trade deal with Donald Trump – is looking foolish. Despite sucking up to the US president with the offer of a state visit, there’s no indication that Air Force One will land in Britain. And if he ever does a trade deal, it is likely to require us to open our markets to chlorine-washed chicken while letting US companies compete with the NHS.

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May’s basic problem was that she had a wishlist, not a deliverable plan. She then went ahead and triggered article 50, throwing away one of the few cards she had in the Brexit talks without securing any concession from the EU. Our former EU ambassador warned the government this would lead to us getting “screwed” – and it has.

The prime minister still isn’t facing the facts. For instance, she says she wants a two-year transition deal, despite the fact that this won’t be nearly long enough to conclude a spanking new trade agreement with the EU. As a result, May is merely shifting the cliff-edge to 2021.

We are told that she is preparing another big speech next month setting our her vision for our future relationship with the EU. If Lancaster House is anything to go by, we should expect the same combination of delusion and dishonesty – when the least the public deserves is realism.

• Hugo Dixon is co-founder of CommonGround and editor-in-chief of infacts.org, making the fact-based case for Britain to stay in the EU