We've often looked at the value of individual political autographs, which the range of values can be particularly great depending on how many papers the political figure in question has signed, which might be a great many or might be a very small number (consider the doomed signer of the Declaration of Independence Button Gwinnett or short-lived President William Henry Harrison).

The eminence of the figure in question is obviously the other key factor. But what if the figure in question doesn't even exist?

This week, a veteran UK politician had a puzzling experience when he contacted the Prime Minister's office at Number 10 about a constituency matter and received a response claiming to be from, and even signed by, a Mrs E Adams.

Sir Gerald Kaufman decided to follow up by calling up, but was told that Mrs E Adams doesn't speak on the phone. In fact, that turned out to be just one of many things she doesn't do: she doesn't exist at all.

The MP noted that his four decades in the job, no other Prime Minister before David Cameron has failed to respond to him personally and described the faked reply as 'extraordinary conduct'. However, the office has claimed the practice dates back to 2005 following a threat to a staff member after she used her real name to sign a reply letter to a member of the public.

Nevertheless, actually signing the name of a non-existent person to a letter seems bizarre. It certainly stands in contrast to the recent auctioning of a personal reply to a US citizen's letter by Barack Obama.