This time last year, the public knew little about Mark Kennedy and the network of police spies in political campaigns. It is in many ways remarkable how much more the public has learnt about these clandestine operations in the past 12 months.

A year ago, on January 10 2011, Kennedy's name first burst out into the public consciousness. Kennedy had been outed initially by activists. The disclosure of his role in a collapsed court case led to a cascade of revelations about the police's secret manoeuvres to infiltrate and disrupt activists over the past 40 years.

The disclosures have shone unprecedented light on a very hidden story of British policing.

We thought that we would step back for one moment and outline what has been revealed in the past 12 months.

As well as Kennedy, seven other undercover police officers have been named or accused. (A ninth, Peter Black, had spoken out in 2010).

Kennedy has gone from being a spy operating deep undercover for years to being a high-profile name - so much so that the BBC listed him as one of their Faces of 2011.

Other spies who have been thrust into the spotlight are Jim Boyling, Lynn Watson, Mark Jacobs, Bob Lambert, and Simon Wellings. Last month, two more were accused of being undercover police officers - Mark Cassidy and John Barker.

The revelations have compelled police chiefs, prosecutors and other official bodies to set up 12 inquiries, all behind closed doors. The establishment is so far resisting launching a full public inquiry.

There have been a series of controversies which have made the covert world of undercover policing a little less covert.

Here are some of the main talking points.

A group of women has launched a lawsuit against police chiefs. They say they were duped into forming long-term loving relationships with undercover policemen and have suffered intense emotional trauma and pain.

Police chiefs have also been accused of authorising undercover officers embedded in protest groups to give false evidence in court in order to protect their fake identities. It was a practice defended by Britain's most senior police officer, Bernard Hogan-Howe.

A major inquiry blamed both prosecutors and police officers for a miscarriage of justice in which environmental activists were wrongly prosecuted. The inquiry by Sir Christopher Rose, a retired high court judge, said prosecutors and police had failed to ensure that crucial surveillance recordings made by Kennedy were given to lawyers representing the activists.

Police chiefs have come under heavy criticism for spending taxpayers' money on infiltrating political groups which were running legitimate and peaceful campaigns.

This article gives more of the big picture.

2011 was a bumper year for revelations. We wonder what 2012 will bring out into the open.