A former Tory peer who has brought a damages action against the police told the High Court today how he was overwhelmed by the “tsunami” of the expenses scandal.

Lord Hanningfield, 72, is suing Essex Police for up to £6,500 compensation over events in September 2011 – days after his release from prison after serving nine weeks of a nine month sentence for false accounting in relation to his parliamentary expenses.

The police, who deny that his arrest, detention and search of his home near Chelmsford were unlawful, were conducting an investigation into expenses from when the peer was leader of Essex County Council.

It was later discontinued without any charges being brought.

They say they were invited into the house before Lord Hanningfield was taken to Braintree police station, interviewed and bailed without any conditions.

Lord Hanningfield told Mr Justice Eady in London that he accepted he made mistakes over his parliamentary expenses but did not ever think he was doing anything wrong.

“But I was convicted by a jury and that’s how life is. It is water under the bridge.”

He said he was surprised and upset when he heard about the Essex investigation and thought the allegation against him “ridiculous”.

“I did not take it that seriously because I knew there was nothing in it.”

He said that recent events had left him traumatised, on the verge of a nervous breakdown and in need of anti-depressants.

“I have given 40 years of my life to public service and the last three or four years have been so traumatic for me that at times I am not able to cope with things.

“It has been so traumatic for me, having to give up everything I did suddenly. It’s been like a tsunami overwhelming me.”

He said that on the morning of the raid, he was woken by the barking of his Pyrenean Mountain dog, who had slept on the floor of his bedroom since the onset of his nervous problems.

“When I wake up, having been in prison, I still sometimes have a job realising exactly where I am. I looked out of the window and saw several cars and a policeman with what I assumed was a warrant.

“I had been out of prison a few days, I was on a tag, I was still in a state of trauma and shock.”

Lord Hanningfield said that he did not invite the police in but did not stop them : “I just let them in.”

He felt he was being hurried and was worried about keeping a medical appointment he had that day and leaving his dog.

Andrew Warnock QC, for the police, said that Lord Hanningfield accepted the police had reasonable grounds for suspecting him of the offence for which he was arrested – for allegedly fraudulently abusing his position in relation to his use of an Essex County Council credit card account.

However, he claimed that they did not have reasonable grounds for believing that his arrest was “necessary” within the terms of the Police and Criminal Evidence Act 1984.

Counsel said that, on the information known to the arresting officer, he had “more than reasonable” grounds to believe that it was necessary and, if the arrest was lawful, it followed that the detention and search were as well.

He added that, if the claim was made out, any award should reflect the fact that Lord Hanningfield had already served time in prison and that, even in his own case, he would have been subject to an interview under caution at the police station.

As it was, he was arrested at 6.45am and, after being allowed to wash, dress and eat, was taken to Braintree where he was held until mid-afternoon.

The hearing was adjourned until Friday.