Five police officers are under disciplinary investigation after they stopped and handcuffed the British athlete Bianca Williams and her partner, the police watchdog has announced. The investigation covers claims that officers breached police standards of professional behaviour relating to use of force, duties and responsibilities, authority, respect and courtesy. The investigation into misconduct allegations will also examine whether the couple “were treated less favourably because of their race”, the Independent Office for Police Conduct announced. Williams, 26, and her partner, Ricardo dos Santos, a Portuguese sprinter, were stopped by officers from the Metropolitan police on 4 July as they drove to their west London home in their Mercedes. The couple were handcuffed while their baby son was in the car in an incident that generated controversy over police conduct and allegations of racial profiling, which the Met denies. It was one of a series of videos surfacing on social media that raised concerns about police tactics and policies. The IOPC said the five officers were under investigation for misconduct. It stressed this did not mean disciplinary charges would follow. The police watchdog said officers faced allegations over their treatment of Dos Santos. “Potential breaches, which will all be thoroughly investigated, include: the manner of some of the officers’ initial approach to Mr Dos Santos; handcuffing Mr Dos Santos initially and keeping him in handcuffs after he had been searched; and his continued detention and whether there were grounds to do so.” In regard to Williams, the police watchdog said: “The potential breaches, which will all be thoroughly investigated, include taking hold of her without first having sought her cooperation with the search; handcuffing her initially and continuing to handcuff her after she had been searched; her continued detention and whether there were grounds to do so.” Williams and Dos Santos are both trained by the former Olympic champion Linford Christie, who accused police of institutional racism. Video of the incident in north-west London showed Williams, apparently distressed, telling officers: “My son is in the car.” Following news of the investigation, Dos Santos told the PA news agency: “We were given no notice by the IOPC that a decision had been made and that they would be making this public today. We have not had any direct contact from the IOPC or any information to understand why they are only considering misconduct and not gross misconduct. We will respond to this tomorrow.” The IOPC regional director, Sal Naseem, said: “Having analysed a range of evidence including police body-worn [cameras], dashcam video and witness statements, we now have a fuller picture of the officers’ interactions with the couple and their child. “As a result, we have taken the decision that this meets the threshold for a misconduct investigation. The allegations will now be investigated thoroughly and independently. “It is important to note that a misconduct investigation does not necessarily mean misconduct proceedings will follow. Decisions on any further action will only be made once our investigation is complete.” The Met said: “The serving of notices does not necessarily mean misconduct proceedings will follow. The officers involved are from the territorial support group. No officer is suspended or subject to restricted duties. The MPS [Metropolitan police service] continues to fully cooperate with the IOPC investigation.” The IOPC also said it would be looking at why the Mercedes was followed and whether the force used was lawful, necessary, reasonable and proportionate. It would also examine “whether there were legitimate grounds for a Merlin report to be created for their baby who was in the back of the car”. Merlin is a database run by the Met that stores information on children who have become known to the police for any reason. Investigators will also examine the accuracy of the accounts provided by the officers and statements made by the Met after the incident. The Met commissioner, Cressida Dick, has said the force apologised to Williams for “the distress it has clearly caused her”. Williams has said she believed the stop happened because of her race. • This article was amended on 8 October 2020. The original headline incorrectly stated that the Met police were investigating the officers; it is the IOPC that is investigating.