Behind one of the greatest tragedies in UK policing history lies an incredible political scandal.

On 17 April 1984, as demonstrators gathered outside the Libyan embassy in London, two gunmen lay in wait inside. At 10.18 a.m. automatic gunfire rained down on the protestors and WPC Yvonne Fletcher fell, mortally wounded.

As his friend lay dying, PC John Murray made her a promise that he would not rest until those responsible had been brought to justice. Thirty-seven years would pass before he was able to fulfil that undertaking.

While researching this moving account of one man's dogged pursuit of justice for a murdered colleague, Matt Johnson uncovered secret-service deals and government duplicity, all part of a plan to force an end to the National Union of Mineworkers' strike. He discovered the real reason Yvonne's killers were allowed to go free and how events that day led to thirty years of growing political control of policing, resulting in the disarray increasingly evident today.

This compelling account pulls seemingly unconnected threads into a coherent - and shocking - whole. It provides startling insights into how decisions taken by our politicians and the actions of our intelligence agencies, supposedly in our best interests, may be anything but.