Secretive justice - is it justice?

"Secrecy, being an instrument of conspiracy, ought never to be the system of a regular government" - Jeremy Bentham (1748-1832).

In 2009, Justice published an interesting and important report on the extent of secrecy which has gradually built up over recent years in English legal proceedings - see Secret Evidence.  This is well worth reading for those who are concerned about modern legal process.

Should Bentham's notion still apply or is it somehow only relevant to a bygone era?  If it should apply, why are there so many exceptions?