THERESA May laboriously struggled to get through her conference keynote speech yesterday after a series of embarrassing problems left the Tory faithful reeling.

Seasoned political reporters said they had never before seen an address from a Prime Minister so riven with mishaps.

The bizarre episodes began when an intruder gave her a P45 live on stage, continued with the PM developing a persistent cough prompting observers to wonder whether she would carry on and ended with parts of the backdrop collapsing.

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The address should have been the highlight of the four-day event in Manchester and was meant to put May on the front foot after a disastrous General Election campaign in which she lost her Commons’ majority and saw Labour’s strength soar.

It also should have made delegates leave feeling refreshed and upbeat.

But instead a sense of unease gripped the hall and Cabinet members sat gloomy faced as May’s poise teetered as she battled to get her words out. “This is excruciating to watch,” tweeted the Scottish business journalist Ian Fraser.

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Shortly before the bizarre problems began, the PM issued an apology to conference goers over the loss of Tory seats at the snap election. She thanked activists for their work leading up to the June 8 vote, before apologising, saying they did not get the victory they wanted “because our national campaign fell short”.

She added: “It was too scripted. Too presidential. And it allowed the Labour Party to paint us as the voice of continuity, when the public wanted to hear a message of change.I hold my hands up for that. I take responsibility. I led the campaign. And I am sorry.”

A few minutes later commotion erupted in the conference hall when a man, later identified as comedian Lee Nelson – real name Simon Brodkin – handing a P45 to May in front of a hall packed with activists.

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He was whisked away by security officers later tweeting that Boris Johnson — who has been at the centre of speculation over whether he will challenge May for the leadership — asked Brodkin to do it. Brodkin was later arrested for breach of the peace.

The stunt raised questions about the PM’s security after it emerged he had attended the conference with legitimate accreditation.

While much of the attention focused on the intruder, the PM’s persistent cough and letters falling off the slogan “Building a Country that Works for Everyone”, May used the 65-minute speech to announce new policies. These included legislation to impose a cap on energy bills, and an additional £2 billion to build “a new generation of council houses”.

But it is understood that the additional cash, for which local authorities and housing associations will be invited to bid, may fund as few as 25,000 new homes over the next five years.

Aides said the draft energy bill to be published next week may never become law, if regulator Ofgem is able to come up with its own proposals for an effective cap more quickly.

After her address she was hugged by husband Philip and Downing Street attempted a damage limitation exercise, insisting May was “happy” with how the speech had gone.

Sources blamed a “conference cold”, the combined effect of 28 broadcast interviews and 19 receptions for the croaky voice which repeatedly forced her to stop.

At one point, she was handed a cough sweet by Philip Hammond to help her carry on, joking that it was not often that the Chancellor gave anything away for free.

After she had finished, she tweeted a photo of a range of throat medications next to a copy of her speech, with the single-word comment “*coughs*”.

After a four-day conference dominated by speculation over Johnson’s leadership ambitions, May made no mention of her Foreign Secretary by name, instead praising the “team” around her in the Cabinet.

She singled out for praise Scottish Tory leader Ruth Davidson, often tipped as one of Johnson’s main potential rivals for the top post.

In a personal account of her motivations for entering politics, May told of her grandmother, who worked as a domestic servant and made sacrifices in the hope of winning a better future for her family.

She said that, even though she and Philip had not been able to have children, she too wanted future generations to be able to enjoy better lives than those of their parents, something she described as “the British dream”.

To a standing ovation she said: “It has always been a great sadness to me and Philip that we were never blessed with children.

“It seems some things in life are just never meant to be.

“But I believe in the dream that life should be better for the next generation as much as any mother, any father, any grandparent.

“The only difference is that I have the privileged position of being able to do more than most to bring that dream to life.

“So I will dedicate my premiership to fixing this problem, to restoring hope, to renewing the British dream for a new generation of people.”