A series of shocking police blunders allowed Nightstalker rapist Delroy Grant free to sexually assault at least another eight pensioners before his eventual arrest, a new report has revealed.

Detectives attempting to snare the gerontophile sex beast failed to follow up basic enquiries allowing Grant to continue his reign of terror for more than a decade.

The IPCC report revealed Grant should have been arrested in 1999 after he was spotted putting on a balaclava, and gloves at the scene of a burglary which was linked to the Nightstalker attacks.

A witness took down Grant’s BMW registration number, which officers traced to his home in Brockley.

However they failed to approach him. He was not questioned about the burglary or asked to give a DNA sample which could have linked him to rapes and burglaries he had carried out since 1992.

Grant was also confused with someone else of the same name already eliminated from the investigation because his DNA did not match that found at crime scenes.

The report said the investigating officer should have realised this Delroy Grant was a different person as he was “appreciably older” than the one already investigated.

The report said officers in the Bromley burglary squad and Operation Minstead – a unit set up to catch the Nightstalker – had failed to communicate which had “potentially dire consequences”.

An Independent Press Complaints Commission inquiry uncovered the errors following the minicab driver’s 27-year conviction in March for burgling, raping and indecently assaulting pensioners in Addiscombe, Shirley, Warlingham, Coulsdon, Thornton Heath and Bromley for more than 17 years.

Despite the fact a burglary in Bromley had the hallmarks of Grant’s previous crimes, the investigating officers did not get details of what was stolen, or get a search warrant for Grant’s address, or recover his vehicle for forensic examination.

A Detective Constable from Bromley, who faced a misconduct hearing over her actions, said she did not look into the burglary further because she thought Operation Minstead had taken over the investigation.

A Detective Constable from the Minstead team said he visited Grant’s address at Brockley Mews but was unable to tell investigators why he had not properly pursued inquiries relating to the BMW.

He said: “[The police] could have arrested [Delroy Grant] for this burglary. We should have arrested him for this burglary. There is no reason that I can give why he wasn’t straightforwardly arrested one morning and interviewed.”

During the three months officers dithered over what action to take over the 1999 burglary, Grant carried out four indecent assaults and two rapes on victims in their 80s in Kent and Croydon.

He was eventually arrested in November 2009. Although he was only charged with 29 crimes, it is believed he could have had hundreds of victims.

Police formally apologised for the blunder after the trial in March.

Commander Simon Foy, head of the Met Police’s homicide and serious crime command, said: “We are deeply sorry for the harm suffered by all those other victims and for our failure to bring Grant to justice earlier.”