In 2003, the BBC screened the controversial documentary The Secret Policeman, in which undercover reporter Mark Daly revealed racism amongst police recruits in Manchester.
Five years on he returns to the subject of racism in the police service for Panorama in The Secret Policeman Returns. Here we take a look back at his original film The Secret Policeman.
The Secret Policeman was screened amid a storm of publicity in October 2003.
Mark Daly spent seven months training as a police officer
Graphic images of police officers engaged in racist behaviour - filmed by undercover BBC reporter Mark Daly - caused a huge public outcry.
The-then Home Secretary, David Blunkett, and senior police chiefs condemned the racism on view.
The acting deputy chief constable of North Wales police Clive Wolfendale said he felt "physically sick" while watching the programme.
The film was commissioned by the BBC in the aftermath of the MacPherson report into the police investigation of the 1993 murder of black teenager Stephen Lawrence.
Published in 1999, the MacPherson report concluded that the Metropolitan police force was "institutionally racist".
David Blunkett pledged to deal with the problem
The Metropolitan police was not the only force affected.
David Wilmot - former Chief Constable of Greater Manchester Police (GMP) - launched Operation Catalyst in an attempt to tackle institutional racism within GMP.
He stated "categorically that there is a will and a determination to succeed".
Police forces across the UK followed suit and promised change.
Daly applied to become a police officer with GMP to investigate at firsthand whether progress had been made and began his training in early 2003.
He spent several months at the Bruche National Training Centre in Cheshire and it was during this period his undercover filming recorded the racism of some of his fellow recruits and trainers.
Daly was then posted to a probationary post in Stockport.
In August of 2003, following a tip-off from an anonymous source, Daly was arrested by police internal affairs officers.
As news of his arrest and the BBC's film came out, former Chief Constable Wilmot was among those to condemn Daly's actions.
Mr Blunkett questioned the BBC's "intent to create, not report" the story.
The BBC defended its motives saying it was the only way to expose the problem.
However, when The Secret Policeman was broadcast, the methods used were no longer seriously questioned.
The damning evidence - which included one recruit seen saying that "Stephen Lawrence deserved to die" - sent shockwaves through the police service.
Recommendations for change
The fall-out was swift. Mr Blunkett called the evidence "horrendous".
The Campaign for Racial Equality launched a formal inquiry. They ultimately found racism still at the core of the service and made 125 recommendations for change.
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Mike Fuller, Britain's most senior black police officer, talks in 2008 about the original film
Ten of the police officers involved resigned. Twelve more were disciplined and three police trainers were removed following a Police Complaints Authority (PCA) investigation, in agreement with the Independent Police Complaints Commission (IPCC).
The IPCC made a number of recommendations for changes to police training nationally - some similar to those used in Northern Ireland to bridge sectarian divides.
Commissioner Nicola Williams - who supervised the PCA inquiry - said "it is vital that the police service supports the need to treat everybody fairly regardless of their race, religion or colour".
Five years on from The Secret Policeman, Panorama's The Secret Policeman Returns shows that even though progress has been made, the problem of racism in the police force is more than skin deep.
The Secret Policeman was broadcast on BBC One on 21 October 2003