The series, based on J.K. Rowling's best-selling boy wizard stories, was nominated for 12 Oscars over its 10-year history, in the art direction, visual effects, makeup, cinematography, costume design and music categories.

Each time it went away empty-handed, to the growing frustration of the cast and crew that worked on one of the most successful film franchises in history.

The final chance came with the concluding installment "Harry Potter and the Deathly Hallows - Part 2", released last year and shortlisted for art direction, makeup and visual effects.

In two of those categories it was beaten by Martin Scorsese's "Hugo", while the makeup award ended up going to Margaret Thatcher biopic "The Iron Lady".

"I think a lot of us look fairly wryly at the politics of the American Academy (of Motion Picture Arts and Sciences), of which I am a member," said John Richardson, special effects supervisor on the Harry Potter movies.

"It does beg the question why did Harry Potter not get recognized at all for the last Deathly Hallows film?" he told Reuters at the press launch of the new Potter studio tour at Leavesden Studios just outside London.

"We got three nominations from the ... Academy for probably one of the best-made and best-grossing films of the year, whereas a Martin Scorsese film, Hugo, which wasn't anything like as successful, won three awards, or was it four?"

In fact it was five -- art direction, cinematography, sound editing and mixing and visual effects.

Deathly Hallows - Part 2 earned $1.3 billion in global ticket sales, according to Boxofficemojo.com, making it the third biggest movie of all time before inflation is taken into account. It was also a critical hit.

Nick Dudman, in the special makeup effects department, agreed that Potter films had been wrongly overlooked.

"We keep losing," he told Reuters. "Potter has been very largely ignored by academies around the world, and it is slightly strange.

"But the work is its own reward in many ways. We make fabulous things, we have a great time doing it."

Richardson said one reason why the Potter films failed to land any Oscars may have been the voting system, whereby the Academy's entire active membership can select winners in every category during the final ballot stage.

The BAFTAs, Britain's equivalent, differ in that all members can vote on eight main categories, but for every other nomination only those with specialist knowledge of that particular field can participate.

"The final (BAFTA) vote is a chapter vote, so the award is voted by your peers, if you like.

"It so happens that we won the BAFTA, but I think it gives a truer critique of the work rather than being voted on by, with due deference to everybody, a lot of people who don't necessarily understand the work or technology that's involved in creating the film."

Deathly Hallows - Part 2 won the special visual effects BAFTA, beating Hugo, although Scorsese's film did trump Potter in the sound and production design categories.

Richardson has been nominated six times for an Oscar, three of them for a Potter movie. He has won once, for "Aliens".

(Reporting by Mike Collett-White, editing by Paul Casciato)

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