Surely it matters that the tapes exist? Outside Bulmer's possession?

Any tapes he might have will be well buggered by now after 30 - 40 years, that's fairly certain. How many bricks does he have these days? Dobermen eat like horses. Besides, if someone did release them he'd get paid as the owner of the rights. I may be wrong in this, but I'm guessing he'd have to take out an injunction against the release, and give a good reason for doing so.

If it was released he'd make money, and it would cost him to try and prevent a release. I believe the expression is 'a no-brainer'.

Regarding the dodgy 'Bright Phoebus' release mentioned above, a comparison of the frequency analyses of the CD and the LP might prove informative.