Major error in train set

GB error collectors have got off to a flying start in 2004 with the discovery of a single imperforate pane of the 47p value in the Classic Locomotives set of six stamps which was issued by Royal Mail on January 13.
The pane comprises 24 stamps (4 x 6) or 12 imperforate pairs if, and when, split. A complete sheet is made up of four panes of 24 stamps, but would most probably been cut and distributed to post offices as single panes.
As GB sheets are litho printed, they would have been sheet fed. This means that part imperforate sheets (typical of gravure web printings) almost certainly don't exist. What it does mean though is that a further three panes of 24 are likely to have escaped the printer De La Rue's checking process. Whether they all got to post offices and were then sold is another matter. So far, just the one imperforate pane has been confirmed.
The 47p value features the 'air smoothed' West Country class 'Blackmoor Vale' at Horsted Keynes Station on East Sussex's famous Bluebell railway. Stamp dealers are already asking £700 for an imperforate pair of the 47p Classic Locomotives stamp less than a month after the stamps were originally issued.