More than 1,000 files on the Guildford Four, Maguire Seven and Birmingham Six, notorious miscarriage of justice cases involving innocent Irish civilians living in England, are to remain secret almost a century longer than they were supposed.

The files were due to open on Wednesday, but are now closed for either 84 or 100 years from their original date. The new opening dates range from the 2050s to the 2090s.

The files are are from a five-year inquiry by retired judge John May that took place between 1989 and 1994 into the wrongful convictions.

Campaigners for the Guildford Four -- Paul Hill, Gerry Conlon, Paddy Armstrong and Carole Richardson -- believe they show that very senior figures were involved in concealing evidence of their innocence for political reasons, and that May’s inquiry was a cover-up.

British barrister and Conservative politician Michael Havers, who represented the Crown in the trial and appeal of the Guildford Four and the Maguire family, later became Attorney General under Margaret Thatcher.

There were also fears that some files have been newly tampered with or even destroyed. Retired lawyer Alastair Logan, who represented the Guildford Four and campaigned for the files to be opened, said there was now no way to know if the files are still intact following their removal and examination.

In addition to the secret files on Guildford, there are also sealed files on the Birmingham Six - Paddy Joe Hill, Hugh Callaghan, Gerard Hunter, Richard McIlkenny, William Power and John Walker – another miscarriage of justice case from the same era of the mid 1970s.