A senior Hertfordshire police officer has been dismissed without notice after he lied about an affair with another police officer.

Chief Superintendent Matthew Thompson was found to have lied to his line manager and to have concealed relevant information from the Head of Professional Standards by a police misconduct panel that concluded today (Friday, 13 February).

Mr Thompson, who is married, had a sexual relationship in 2024 with a female police officer, referred to as Witness A. The relationship took place outside of work.

While Witness A was outside of Mr Thompson's line management chain, her spouse, referred to as Witness B, was within Mr Thompson's line management chain.

During a six-day hearing, the misconduct panel found that Mr Thompson's actions in hiding details about the extramarital relationship over an extended period of time amounted to gross misconduct that was so serious it justified dismissal from Hertfordshire Constabulary.

The panel's chair, Assistant Chief Constable Nicholas Davison, said Mr Thompson had "set out to conceal as much of the relationship as he could" and had been "dishonest whilst on duty".

Dijen Basu KC, representing the Appropriate Authority that brought the case against Mr Thompson, told the panel that Mr Thompson's "credibility is in tatters" after the "very serious and depressing" case.

Mr Thompson had accepted that his actions amounted to misconduct, but not to gross misconduct.

He began his police career as a special constable in 1995 and rose to a senior rank within Hertfordshire Constabulary.

Among his responsibilities was acting as an on-call gold commander, leading the police response to critical incidents in Hertfordshire. He received four commendations during his police career, including for rescuing an elderly man from a burning building in 2002. 

The sexual relationship between Mr Thompson and Witness A was discovered by Witness B, who informed the police force.

But over the course of several weeks after Witness B's discovery, Mr Thompson failed to tell his line manager or the Head of Professional Standards about the full circumstances of the relationship. By the time he was facing a formal misconduct investigation, he had still not disclosed all the relevant details.

Mr Thompson admitted during the hearing that he had lied to his line manager, Assistant Chief Officer Cat Hemmings, when she asked him a direct question regarding a particular detail about the affair.

However, Mr Thompson told the panel that his lie had not been "deliberate" and claimed that the "intention" of his telephone conversation with ACO Hemmings had been to outline to her only the details of what had been reported by Witness B, rather than any other details.

Mr Thompson said he "had no sense of being rational at that time" and added: "As the call progressed, I was just feeling worse and worse and worse and just emotionally collapsing.

"I was just in absolute pieces and it just continued forever."

He said he had not expected to be asked questions about the relationship during the call, and Matthew Butt KC, representing Mr Thompson, claimed that he "gave an untruthful account as the result of real unfairness from his supervisor".

Mr Butt said it had been an "error" for ACO Hemmings to play both a "fact-finding role" and a welfare support role during that conversation.

The panel, however, concluded that ACO Hemmings had followed the police's national decision model during the call and that her response had been "reasonable and proportionate".

Panel chair ACC Davison said that during the call with ACO Hemmings, Mr Thompson had "acted with clear intention and with specific outcomes in mind".

"Despite [his] emotional turmoil, he was still able to choose what information to disclose and how to present it," ACC Davison said. "Although [Mr Thompson] was highly distressed, he was still capable of making deliberate strategic decisions."

Shortly after Mr Thompson's conversation with ACO Hemmings, he spoke about the affair with Detective Chief Superintendent William Hodgkinson, Head of Professional Standards across Bedfordshire, Cambridgeshire and Hertfordshire.

That conversation and an ensuing message resulted in DCS Hodgkinson telling Mr Thompson that it would be "useful" if he could "provide an email with the detail of what has happened".

Mr Thompson claimed that he believed DCS Hodgkinson had wanted a more limited account of particular details relating to the affair, but the panel concluded that he had "failed to report critical information". 

Mr Basu said the officer had "only admitted what he knew was already available to the professional standards department". Mr Basu added that Mr Thompson had had to be "dragged to a realisation" while giving testimony this week that he had acted without honesty and integrity.

Mr Thompson told the panel he had not intended to "actively mislead" either ACO Hemmings or DCS Hodgkinson, and said he was "sorry" that he had not given a full account of the affair at the time.

Mr Thompson, who became emotional at times while giving testimony, told the panel: "I've been completely remorseful and apologetic. It's so out of character. I'm ashamed of what I've done.

"I'm sorry for … the hurt I've caused [and] the inconvenience I've caused to the organisation. I'm just sorry for putting everyone in this horrible position."

But Mr Basu suggested that Mr Thompson was instead showing "self-pity", and the panel's chair, ACC Davison, concluded that Mr Thompson's remorse was "self-centred and focused on the consequences to him".

ACC Davison added that Mr Thompson had "consistently resisted admitting to any real level of culpability for the impact of his actions".

The panel found Mr Thompson had broken the standards of professional behaviour relating to honesty and integrity, orders and instructions, and duties and responsibilities.

ACC Davison said: "Discipline and good order was impacted. Failure to disclose full details impacted on the force's ability to manage the situation. The public [will] be rightly concerned about the impact on the organisation and the management of the force."

Mr Butt, representing Mr Thompson, had argued that his client's actions should "be viewed in context and in what can fairly be described as exceptional circumstances".

Mr Butt said those "exceptional circumstances" included Mr Thompson's "state of mind" from the time of his call with ACO Hemmings onwards.

"This is not someone who was thinking and acting in a rational way," Mr Butt said.

The panel accepted that Mr Thompson was "a capable senior officer" who previously had "an unblemished record" as a police officer, and noted that character statements suggested he is "a man of integrity and decency".

But, announcing the panel's findings, ACC Davison said: "A good person can fall into error.

"It is only in times of strain that credibility may truly be tested.

"The officer's sense of self-preservation overrode his otherwise honest nature."

Mr Basu told the panel: "This is not a case about morality.

"The case is about the fact that police officers are always … honest and act with integrity, and do not compromise or abuse their position.

"[Mr Thompson] was dishonest. He acted deceitfully and not with integrity. He did compromise and abuse his position.

"He fell far too short of the standard, far too many times, with far too many senior people … for far too long."

The panel was not required to make a ruling on a further allegation that Mr Thompson had failed to act on serious safeguarding concerns relating to Witness A.

They concluded, however, that if they had been required to make a determination, they would have found that the allegation was not proven on the basis that they were "not satisfied" that Mr Thompson had "any serious belief" that such a safeguarding concern existed.

The panel concluded that dismissal without notice was the only outcome that met the seriousness of the misconduct.

Mr Butt had argued that the officer should have instead been given either a final written warning or a demotion and offered "a second chance" – but the panel found that other options "would fail to maintain public confidence in the police". 

Mr Thompson will also be added to the College of Policing's barred list.

Following the hearing, Hertfordshire Chief Constable Andy Prophet said: "This officer's behaviour clearly fell well short of what is expected of a serving Hertfordshire police officer and is further exacerbated as he is an individual with 27 years' experience and of chief superintendent rank.

"Police officers and police staff are rightly held to the highest standards of behaviour and professionalism. We cannot condone lying or other breaches in conduct.

"I want to reassure the residents of Hertfordshire that I take these standards of behaviour incredibly seriously.  

"It was heard that this officer had previously had an impeccable record of service, but anyone falling short of our high professional and ethical standards has to accept the consequences of their actions.

"Across our force, we work hard to ensure that all officers and staff know what is and is not acceptable and how to confidently call out poor behaviour."

The misconduct panel's outcome is subject to appeal.