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A detective inspector at Devon and Cornwall Police says the force is "unrecognisable" to the organisation he joined 30 years ago.
Praveen Naidoo's early years in the force were marred by racism but he says the force has changed "massively and positively" to become a place he is proud to work.
The DI is now speaking about his experiences of racism within the police force as part of Black History Month.
"My opening experience of Bideford police station was being taken up to the bar by my sergeant," he told ITV News West Country.
"There was a DC who was worse for wear, and his opening remarks were, one could say, less than racially sensitive towards me.
"That set the context probably for the first two to three years of my career."
He said while the overwhelming majority of people are decent, his experience showed him racist behaviour needs to be challenged.
"If you don't challenge poor behaviour, prejudice can actually become quite cancerous within an organisation," he said.
"People need to feel empowered to be able to challenge behaviour which is inappropriate, to create an environment which is safe and welcoming and warm for those people involved."
DI Naidoo described a report after the murder of Stephen Lawrence as a "watershed moment" for the police.
He said: "Devon and Cornwall Constabulary - together with, I would imagine, every other force in the country - took a long, hard look at itself and things began to progress positively and very quickly."
It is a change DI Naidoo says is "ongoing", adding: "The organisation has changed massively and positively. It is unrecognisable now to the organisation that I joined - and it's one that I'm particularly proud to be part of."
Now he says he works with a "fantastic" team.
"I'm no longer that junior PC walking in and wondering how my day is going to be - I'm walking in there and I'm the boss.
"That gives me an immense sense of pride, particularly to those individuals who, quite frankly, barely tolerated me."
Now, he says he focuses on making the workplace a safe place to work.
He continued: "People shouldn't come into work feeling the environment is hostile to them because they happen to have a particular colour skin, because of their sexuality, because of their gender.
"People should be able to come to work and do the job they are paid to do and engage in a professional way and be accepted for who they are as individuals and for the skills that they bring to the organisation
"And within the team that I have, we've got a wealth of skills, much of which I suspect if we'd stayed where we were back in the 90s, we would not have, because those individuals would not have wanted to become part of our organisation back then."
DI Naidoo, who is active on social media and posts on Twitter as @DetectiveNaidoo says he would encourage anybody considering a career in policing to think about joining Devon and Cornwall, whatever their background.