While searching the fare spectrum for London - Birmingham, I found these but the main BRFares listing(at the bottom of the page) says "Not normally available for purchase." When are these tickets available and how does one buy them?
When a fare needs to exist in the database but mustn't be sold to passengers, they'll usually mark it as special by setting the price to 5p, 10p, or something ending with .99 (since all rail fares are supposed to be multiples of 5p). They usually exist in the database for bookkeeping purposes when TOCs might want to issue "special" fares - in this case, when Virgin want to sell rail travel as part of an "International Excursion", as mentioned by @MJeffryes. They need a fare in the database presumably so they've got something against which to issue reservations, etc., and to keep track of how those seats were sold - but they're presumably for use in conjunction with promotions selling a large international trip (for considerably more than 10p!) and have no meaning on their own.