Harry Potter, the apprentice wizard, continues to work his magic on Bloomsbury Publishing, which yesterday reported a 78% rise in revenues for the first half of the year to £11.4m, writes David Teather .

The Harry Potter books, written by JK Rowling, above, were intended for children but have gained a large adult following.

The four titles occupy the top slots in many bestseller lists and sales of up to 4m from the new book, Harry Potter and the Goblet of Fire, will be recorded in the second half of the year.

Shares in the company added 12.5p to 850p, up from 150p 18 months ago.

Nigel Newton, Blooms bury's chairman, said it was "clear to everyone" the impact the series had made on the firm but said much of the first-half growth was attributed to other titles.

Joanna Trollope's Marrying the Mistress and Anil's Ghost, Michael Ondaajte's novel, were other bestsellers on its list.

The business turned a loss of £103,000 last year into earnings of £273,000 in the six months to July.