Relatives of those killed in the 1994 Chinook helicopter crash have delivered a handwritten letter to Downing Street saying they have endured decades of “grief, unanswered questions and institutional silence”.
They are also seeking a meeting with Prime Minister Sir Keir Starmer to voice their concerns in person.
The Chinook Justice Campaign has launched a petition which has been signed by more than 47,000 people calling for a public inquiry.
Twenty-five intelligence experts and four special forces crew were killed when the helicopter crashed on the Mull of Kintyre, en-route from RAF Aldergrove in Northern Ireland to Fort George near Inverness, on June 2 that year.
The incident was initially blamed on pilot error before this was overturned in 2011.
The Ministry of Defence says the “tragic accident” has already been subject to six inquiries, including an independent judge-led review.
The handwritten letter was delivered by Nicola Rawcliff from Norfolk, whose brother Chris was killed in the crash.
The letter to Sir Keir says: “We are writing once again to appeal for a public, judge-led inquiry into why our loved ones were allowed to board a helicopter that was not airworthy – and why key documents relating to the crash have been sealed for 100 years.
“For over three decades we have endured grief, unanswered questions and institutional silence from the Ministry of Defence.”
The campaign had earlier published a list of 110 “unanswered questions” about the crash, including one on who authorised the mission.
A Ministry of Defence spokesman said earlier: “The Mull of Kintyre crash was a tragic accident, and our thoughts and sympathies remain with the families, friends and colleagues of all those who died. We understand that the lack of certainty about the cause of the crash has added to the distress of the families.
“We have now received the Chinook Justice Campaign’s formal claim for a judicial review of our decision to reject the demand for a judge-led inquiry into the circumstances of the crash.
“Our focus is on responding to that claim and to the allegations contained within it and we are unable to comment further at this time.
“The accident has already been the subject of six inquiries and investigations, including an independent judge-led review.”
