A pilot police scheme to use spit hoods on people in custody in detention areas across London will be reviewed after the Mayor of London entered the debate surrounding the controversial decision.
The Mayor's office said: "Any attack on officers carrying out their duties is completely unacceptable, and the use of protective equipment is sometimes necessary.
"The decision on whether to use intrusive tactics is a highly emotive one and should be informed by public engagement.
"We will be discussing the details with the Met and will consult closely with them, and see what further consultation may be appropriate, ahead of any pilot."
Mayor's interference is 'appalling'
However, Mr Khan's decision to step in has not been backed by all at City Hall.
Conservative Party London Assembly member Keith Prince said: "It is appalling that the Mayor has chosen to interfere with police operational matters and block the use of spit hoods.
"Has he forgotten he is no longer representing those who make claims against the police but in fact representing the police themselves?"
He added: "The decision to use these hoods would have been taken as a result of a risk assessment showing that officers were at risk of infection transferred by spitting. I myself know of one serious example of that.
"What risk assessment has the Mayor based this intervention on and what alternative safeguards has he put in place to protect officers on the front line?"
'Spit hoods like something out of horror stories'
Director of Liberty, Martha Spurrier, called the use of the mesh hoods "primitive, cruel and degrading", and something which "belongs in horror stories".
Amnesty International campaigners added "serious questions need to be raised" about their place in modern policing.
A police statement read: "A pilot within the controlled environment of custody suites had been arranged for October.
"This was agreed by the Metropolitan Police Service Policy Forum in February, which is made up of officers and staff from across the organisation.
"A consultation process regarding their use has taken place and involved community advisors from Newham's Independent Advisory Group, in addition to local magistrates and judicial staff.
"However with a new administration coming into City Hall since then, the MPS has listened to concerns and will consult further before starting any pilot."