This remarkable news is announced in 'first', Royal Mail's colourful pamphlet about new stamp issues, but it is hidden on page 3 of the Diamond Jubilee issue:
Now my copy of 'first' arrived this morning but my correspondent only learned about this from a friend and hasn't yet had his own. If he had, he would also see that the order form, predictably, indicates that the usual handling fees will apply - £1.45 UK, £1.55 Europe, £2.15 Rest of World.
UPDATE from Royal Mail Day 2 6.30pm (really!): "we will still process orders for FDCs at Tallents House for those people who received the communications late."
UPDATE (Day 1): other writers have said that the situation is worse even that we thought. At the time of writing some Post Offices cannot sell the packs today, the day of issue, because the pack is not yet on their till system (Harlow, Cambridge so presumably all.) This probably means that they won't sell FDCs either. (see comments, also)There is likely to be considerable demand for FDCs produced by dealers!
LATER: Norwich PO was able to sell packs mid-afternoon on 1st day.
Day 2: Bought my Flags this morning without the problems that I had with the pigs, although £20 notes still not accepted (even for a £100+ purchase - they are normally restricted to purchases over £10 anyway).
I noticed that a customer using the 'post it now' menu for postcards for Hungary (87p) received 20g Europe Faststamp (which is also 87p). That's the first time I've seen a Faststamp produced from the 'post it now' menu other than the 10g Worldwide (which is also currently 87p!).