Morning Mike,
Talking about MOD disposal of unwanted material, I think a massive amount of gear went into the sea years ago, or into the ground ... Just up the road from me is a former RAF airfield, I worked with a guy for many years who was stationed there with a resident MU, well the "environmentally unsound" methods of disposal there (and I guess all round the country) were very much out of sight, out of mind, unwanted/obsolete parts/engines/ all types of fuels/ammo/ ANYTHING ... dig a big hole, bury it!
Going back 15 years ago when the MOD sold the site, the contractors had quite a job clearing out the buried dump and removing tons of heavily contaminated soil, job done ... or so you might think, when I bumped into the same chap a few years back and told him the dump had been cleared, he just looked at me with a rye smile and said which one!?
Like so many former airfields around the country, this site is due for development, so wait for the brown sticky stuff to hit the fan when the ground works starts!