It is one of the pieces of information the VM forum team can/do ask as an alternative to letters from the customer's support password.
It would only be asked by, and should only be supplied to, a VM forum team member via the private messaging system on the forum. VM forum team members can be identified by the VM infinity logo next to their name and the words 'Forum Team' under their name. They are listed here
https://community.virginmedia.com/t5/custom/page/page-id/WelcomeGoodFolk
