A Tory MP's top aide was today found not guilty of raping a woman in the parliamentary office of his boss after a boozy night out.

Samuel Armstrong, 24, the chief of staff to South Thanet MP Craig Mackinlay, was alleged to have raped the woman, who also worked in Westminster, in the early hours of October 14 last year.

The pair - described as "quite good friends" - had been drinking together earlier that evening at the Sports and Social Bar in Parliament with others.

Today a jury at Southwark Crown Court found Mr Armstrong not guilty of two counts of rape, one count of assault by penetration, and one count of sexual assault following five-and-a-half hours of deliberation.

He fought back the tears as the verdicts were read out and, after leaving the dock, he was comforted by his father.

Judge Jeffery Pegden QC thanked the jury for their work after the verdicts were returned.

During the trial Mr Mackinlay compared his and Mr Armstrong's relation to like "father and son" and never saw him act inappropriately in front of female staff.

The trial heard after the sexual encounter the woman, who cannot be named for legal reasons, was found wandering the corridors of Westminster by cleaners just after 2am.

After going to police that morning, the complainant went to The Sun newspaper with the story, to get a "sympathetic write-up".

The complainant also had a history of mental health problems, had been treated from depression and panic attack and had been on antidepressants at the time of the encounter.

During cross-examination Sarah Forshaw QC for the defence, said the complainant consented to sex, but panicked when she found herself alone in the Houses of Parliament without a proper pass at 2am.

Ms Forshaw QC said: "I do not suggest you have deliberately lied to get Sam Armstrong into trouble.

"I suggest you told a lie at the time, and once you told it, you knew you couldn't take it back."

After drinking in the parliamentary bar, the pair went up to the Lords Office where they continued to drink with two other people.

They want back to Mackinlay's office at about midnight with and CCTV showed them walking through Westminster Hall arm in arm and dancing together, with the woman seen pirouetting around Armstrong.

She claimed she fell asleep on the sofa in the office and was awoken by Armstrong kissing her neck and grabbing her breast before he took off all her clothes and raped her.

However, giving evidence, Armstrong said: "We sat there talking for a while.

"After that had gone on for a while she reached back her arms and smacked her hands on the side and got up and said 'dance with me'."

They danced and eventually kissed before ending up on the sofa where he tried to take her bra but failed, and she "started to laugh" and took the garment off himself.

He described her making "all the appropriate noises" during sex and she even threw papers off a nearby desk before bending over so he could enter from behind.

The music playing on his his laptop changed track and "killed the mood a bit" so the complainant got up to change the song.

Armstrong said: "She then said to me 'well some people are going to think you've taken advantage of me'.

"It was in a quite a teasing voice. And I said, 'I'm not sure anyone could come to that conclusion'."

The court heard she then got on top of him and they continued to have sex on the sofa for a few more minutes.

While she was "bouncing on top" of him he asked her "how does the size suit the lady?", which he heard a tailor say and to which she replied 'it suits the lady very very well'.

"We were joshing around, I was being a bit of a prat."

After they finished he was "out of puff" and asked her if she wanted to go back to his flat, but she declined as she had work in the morning.

Armstrong said: "I asked her, after a little while, I said 'are you sure you don't want to go back to mine?' And she went 'nah, but I have had fun'.

"I said 'well we'll have to do this again some time' and she said 'yeah, sure I'll see you around'. It seemed a bit corny when she said it."

Under cross-examination he told the jury he was attracted to the complainant and at the time thought there could be a romantic encounter.

When asked whether he forced the alleged victim to give him oral sex he said: "I don't think I would put that piece of my anatomy between someone's teeth if they didn't want it to be there."

He said the moment police came to door to arrest him "like someone punched me in the stomach", and thought there must have been some sort of mistake."

"I have been unable to work, unable to sleep for several weeks, I have been unable to eat and I've been very sick" - Sam Armstrong

Describing the impact the allegations have had on him he said: "It was an act of enormous foolishness and as a consequence I have had the worst year of my life.

"I have been unable to work, unable to sleep for several weeks, I have been unable to eat and I've been very sick .

"While what I did was foolish, the point is I am innocent of this for and whatever reason someone has made this horrible horrible horrible allegation.

"I've been embarrassed and I have suffered and I am never ever ever going to get my career back, that is not the point.

"The point on this allegation someone is trying to send me to prison for a very long time for something I didn't do."

Since the allegations Armstrong was suspended from his job and from the Conservative Party.

Speaking after the hearing, Mr Armstrong gave a short statement to the press outside Southwark Crown Court, and referred to issues of disclosure in the case.

He said: "My whole life has been turned upside down.

"For a year I have not slept or eaten, and I was innocent.

"Were it not for the fact that crucial evidence was disclosed to my defence team just eight working days before trial, there could well have been yet another miscarriage of justice in this case."

It is understood the material he refers to are the phone and medical records which the complainant initially refused to hand over to police.

It is also believed Armstrong's lawyers had been waiting up to nine months for the material.

Mr Mackinlay added: "I'm obviously delighted that Sam has been cleared. I had no doubt as to his innocence throughout.

"This has been a horrendous time for both Sam and his family and questions do need to be asked about the time it took to progress this case.

"And in a week where we’ve seen various rape trials collapse because the authorities had failed to disclose crucial evidence, I do think we should also re-consider extending the right of anonymity to rape defendants until charge or conviction."