Police officers were employees of the police force. They were also called cops, coppers, bobbies, policemen or policewomen.
Yasmin Khan preferred the term "police officer" over "policewoman", and frequently had to correct her father over this matter. (TV: Arachnids in the UK)
By 2018, some police forces fitted their officers with uniform cameras, as part of their uniforms, in case of lawsuits and for data records. (TV: The Tsuranga Conundrum)
Constable was a rank of police officer, (TV: Everything Changes, The Cambridge Spy, et al.) as was Sergeant. (PROSE: Long Time Dead)
Mason was a police officer in 1955 Montgomery, Alabama. (TV: Rosa)
Gwen Cooper was a police constable before joining Torchwood Three. (TV: Everything Changes)
Andy Davidson, Gwen's former police partner, and ally to Torchwood, (TV: Adrift, The Blood Line, AUDIO: More Than This, et al.) was promoted to Sergeant by the time he resigned from the force. (AUDIO: The Empty Hand, PROSE: Long Time Dead)
When she met the Thirteenth Doctor, Yasmin Khan was a junior police officer with Hallamshire Police, in her second year of probation. (TV: The Woman Who Fell to Earth)