Entertainer Michael Barrymore's arrest over the death of a man at his home was unlawful because the officer involved had not been fully briefed, court papers filed by Essex Police admit.
The former star is suing the force for damages after he was detained in 2007 over the death of Stuart Lubbock.
Mr Lubbock was found dead in a swimming pool at Mr Barrymore's home in 2001.
In High Court documents, the force admits the detective who was supposed to arrest the star was delayed.
The force said it wanted to question Mr Barrymore, whose real name is Michael Parker, and two other men over the rape and murder of Mr Lubbock after new evidence emerged.
Post-mortem tests found the 31-year-old butcher had suffered severe internal injuries indicating sexual assault and his bloodstream contained ecstasy, cocaine and alcohol.
Mr Barrymore and the other men were arrested and later released without charge.
In its defence document, Essex Police said: "The arrest of the claimant was unlawful only by reason of the fact the arresting officer, PC Cootes, was not fully aware of the grounds for arrest... and not by reason of a lack of reasonable grounds to suspect the claimant."
PC Cootes, who was carrying out covert surveillance at the property where Mr Barrymore was staying in 2007, was ordered to make the arrest when the designated officer, Det Con Sue Jenkins, was delayed.
"Since the claimant would have been lawfully arrested but for the said delay, he is entitled only to nominal damages for false imprisonment," the defence document added.
Mr Barrymore's lawyers said police did not have reasonable grounds for suspecting him of the rape or murder of Mr Lubbock, and the arrest was unlawful and "wholly disproportionate and unreasonable".
Their court documents also said Mr Barrymore "suffered loss and damage namely distress, shock, anxiety and damage to his reputation".
He has also claimed his career suffered because of the police handling of the case.
Essex Police said if earnings had been lost, it would be because of "matters outside the defendant's control", including that a young man had been found dead in his swimming pool which had "inevitably" led to a police investigation and inquest.
A decision will be made in the New Year by a High Court judge about compensation Mr Barrymore may receive.
The Barrymore/Lubbock case
- March 2001: Stuart Lubbock died at Michael Barrymore's former home in Roydon, Essex
- October 2001: Following a police inquiry into the death, Michael Barrymore is given a caution for drugs offences and allowing his home to be used for smoking cannabis. No further charges are brought
- February 2006: Mr Lubbock's family are "blocked" from launching a private prosecution against the entertainer after a district judge rules there is insufficient evidence
- June 2007: Mr Barrymore is arrested along with two other men on suspicion of serious sexual assault and murder
- September 2007: Crown Prosecution Service announces that Mr Barrymore will not face charges
- February 2009: The Independent Police Complaints Commission (IPCC) inquiry upholds six of 36 complaints and allegations made by Stuart's father, Terry Lubbock. The IPCC finds two pieces of evidence - a pool thermometer and a door handle - went missing after Stuart's death
- March 2011: Ten years after Mr Lubbock's death, police make a new appeal for information on the case
- April 2013: Mr Barrymore lodges a claim for damages for unlawful arrest and false imprisonment with the High Court