The idea is that interested visiters will pay £5 to park in the NT car park and walk across wet fields to the visiters center (only to find it closed.)
I watched them bringing old tyres out of the hill today, probably from the old Silbury garage which was demolished after Atkinson left.
Atkinson left the tunnel open for over a year so all sorts of crap was probably thrown inside.
PeteG
Ps. Updated photos on my website here http://www.users.myisp.co.uk/~gtour/Silbury2007.html