Clattenburg's fight to clear his name over allegations of using "inappropriate language" towards Chelsea stars John Obi Mikel and Juan Mata witnessed a new twist on Tuesday when police launched a formal investigation into the matter.
The Metropolitan Police confirmed they had acted on a "complaint" from the Society of Black Lawyers after the European champions accused referee Clattenburg of using comments understood to have been interpreted as racist in the club's acrimonious defeat to Manchester United on Sunday.
Press Association Sport understands the 37-year-old completely denies the allegations against him, which are also the subject of a Football Association investigation. Clattenburg and his fellow professionals were said to be shocked and angered by the claims as the refereeing fraternity rallied around their colleague.
There were also suggestions of seething resentment in some quarters at the way Chelsea had made their complaint against Clattenburg public and a desire to see strong action taken against them if the official was cleared.
That could take weeks or even months after the police became involved in proceedings less than 24 hours after the FA's investigation began. Chelsea themselves could yet make a criminal complaint, having appointed an external legal team to conduct their own probe, something which was expected to conclude on Tuesday.
And the FA may be forced to postpone their inquiry if the police request they do so, something they came under heavy fire for during the year-long John Terry scandal. The Metropolitan Police became embroiled in their second high-profile football racism case in 12 months after the man behind the mooted black players' breakaway union, Peter Herbert, wrote to them demanding they investigate Clattenburg.
Herbert defended his intervention, telling Sky Sports News: "What we don't want is for it to be swept away under the carpet. It must be subject to a full and proper investigation. It is to lend some seriousness and some weight behind what is happening in football."
Herbert admitted his complaint was based on reports rather than first-hand evidence but added: "We weren't there but we don't need to be there in order to report an incident. This appears to have had some cogency and so it needs to be addressed as a matter of urgency.
"I think the Met Police have huge resources, expertise, and I have no doubt that this matter will be resolved and the truth will come out. If we've got this completely wrong then, of course, the police will tell us."
Source: PA
Source: PA