Books by World War II aviation historian Dilip Sarkar are now so popular with enthusiasts they are changing hands for £1,000.

The 42-year-old Worcester author, well known for his books on the Battle Of Britain and its Spitfire heroes, published his first book, Spitfire Squadron, in 1990.

He went on to set up his own publishing company, Ramrod Publications, and many more titles followed, his latest being Johnnie Johnson: Spitfire Top Gun, Part Two.

"We usually do limited editions of 100 of each new title, containing a sticker inside the front cover, with the authenticated signatures of Spitfire pilots," said Mr Sarkar.

"They usually sell fairly quickly and it goes a long way towards paying the printing bill. I always knew they would be worth a lot of money one day, but I had no idea it would be this much.

"They are selling for between £500 and £1,000 on the internet.

"There was one that wasn't even one of our genuine limited editions being sold for £100 a throw.

"I wrote a book for the Douglas Bader Foundation and these fake limited editions were being sold on the pretext that the money was going to the Foundation, but it wasn't."

At the launch of part two of his Johnnie Johnson trilogy at Worcester Guildhall on Saturday, Mr Sarkar sold around 200 books, including softback versions of part one.

"Printing it in softback has given it a new lease of life. We had to get the printer to bring some over from Malvern on Saturday," he said.