It's 'chunky' compost, recycled from local brown bins, then sold back to us by North Herts District Council, marketed as 'Ace of Herts' at £4 per bag :o
Not willing to be stitched up in such a fashion (and far too tight), I managed to convince one of the local farmers to drop his load ::) at our plots
Strangely although the public are charged £4 per bag, the local farmers get it for free (because the recycling plant needs the space), and only need a trailer big enough to take the minimum load of 13 tonnes
Hence our whopping great pile only cost what it took to cover the drivers time and a bit of diesel, and should last us 3 years or so :P