In a letter to the Guardian newspaper on Thursday, 19 July 2007, Lord Avebury, owner of Silbury Hill, writes, "Placing a foreign object in the monument offends conservation principles, as well as the spiritual beliefs of some people. Describing the object as a time capsule means that EH expects it to be retrieved at some future date, requiring further tunnelling, yet the current works have been undertaken to correct the mistakes of past excavations."*
Leaving alien objects in Silbury (whether a time capsule, the Atkinson door, lintel etc) blatantly contravenes accepted principles of conservation (not to mention offending the spiritual beliefs of some and the ethics of others. In light of current conservation/structural problems at Silbury, and the fact that future tunnelling into the monument to retrieve a 2007 'time capsule' is now inconceivable, will English Heritage concede, and announce via its Silbury Hill update website, that plans to leave alien objects in Silbury have been abandoned.
* http://www.guardian.co.uk/letters/story/0,,2129468,00.html