The brother of a private detective who was brutally murdered has welcomed the appointment of a new expert to the panel investigating how police handled the case.

Daniel Morgan was found dead with an axe lodged in his head in a south London pub car park in 1987 – a notorious case linked to police corruption which has been subject to five failed probes.

Scotland Yard has previously apologised to the family after admitting that corruption in the original investigation was a major factor in the failure to secure any convictions.

Mr Morgan’s family have longed campaigned for justice, and, in May, home secretary Theresa May announced a judge-led independent panel to probe police failings over the matter.

Now a socio-legal researcher from the University of Manchester, Dr Graham Smith, is set to join the panel tasked with shining a light on the murder.

Alistair Morgan, Daniel’s brother, who lives in Gee Street, Finsbury, said: “It’s an excellent appointment. We have been closely involved, because my brother’s case is so controversial and our trust in the authorities has been so seriously undermined.

“Dr Smith has enormous experience and was involved in investigating corruption in Stoke Newington police station in the 1980s. Daniel’s murder is probably the single worst case I have ever heard of.

“The Met has admitted corruption in the first investigation, but in my view it went a lot further than that.”

Dr Smith said: “The home secretary’s appointment of an independent panel to review the circumstances and subsequent investigations of the death of Daniel Morgan is a tribute to the Morgan family’s campaign for justice. I am honoured that the family and the home secretary have put their trust in me to help uncover what happened more than a quarter of a century ago and why justice has been denied for so long.”

Dr Smith, who has served as a consultant on police complaints to the Council of Europe commissioner for human rights since 2008 and is recognised as an international expert on police accountability, will be conducting research for the panel.

The panel’s other members are its chairman, retired judge Sir Stanley Burnton; criminologist Silvia Casale; and former police officer Michael Kellett.