I also missed the sale - due to illness I was ordered to stay in bed.
Dave official website threatens to prevent people to enter if it appeared that ticket was resold :
"Please note that anyone purchasing a ticket from any unauthorised site or seller will not be granted admission. The restrictions on ticket sales, including named purchasers and photo ID required for entry, are designed to restrict ticket sales to genuine fans and not those seeking to profit from resale. Official outlets are: the Royal Albert Hall box office, seetickets.com, ticketmaster.co.uk, eventim.co.uk, and stargreen.com."
I guess that a small number of tix will put on sale.
At least in France this is mandatory, there is a 50 tix - or so - obligation to be sold on box office on the day of the show.