Colin Knowles, part of the BMC initiative 'Climb Bristol Project' gives us more details:
"An 8mx8m section of the cliff immediately left of Halcyon Days' has collapsed - littering 100 cubic metres of blocks on the slope uphill of the start of Unknown Wall. Access to all the Unknown area, apart from Upper Wall, is closed i.e. access is not permitted to any routes commencing from any part of the flat ground and wooded slope behind the roadside stone wall. Signage/taping is in place top and bottom.
Apart from the threat from precariously loose boulders on the slope there are signs of serious instability to the cliff right of the rockfall (ie the cliff containing Halcyon Days'). Consultant geologists and contractors are in the process of assessing the site and will formulate a remediation plan. These works will have a significant effect on the climbing here. The land beneath this section of the cliffs is now known to be private (and the rockfall has raised liability concerns).
All climbers are asked to stay clear of the area as requested."
Keep up with the developments on the Climb Bristol Project Facebook Page which is updated frequently.
More details on the project can be found on the BMC Website