Harry Potter and the howlers

The film has been smashing box office records since it opened last week.

But although Harry Potter and the Philosopher's Stone cost £100million to make and promote, eagle-eyed film fans have already spotted at least a dozen on-screen howlers.

They range from shadows that are cast in the wrong direction to a now-you-see-it, now-you-don't cat.

The errors were picked up by the website movie-mistakes.com, which currently lists 10,833 mistakes in 1,638 films.

After his dramatic battle with evil Lord Voldemort, Harry has several scratches on his face, including a particularly large one on his chin.

When Professor Dumbledore visits him in the school hospital, the marks have disappeared. Later, the chin scratch returns - and has somehow got bigger.

In the scene when Harry and his friends Ron and Hermione sneak past three-headed guard dog Fluffy, the huge hound wakes up and dribbles all over Ron's shoulder.

However, when they fall through the trap door into the Devil's Snare, Ron's soaked jumper is now completely dry.

When Harry removes his invisibility cloak in front of the Mirror of Erised, it promptly disappears - although it can be clearly seen when not in use during other scenes.

In the scene when Harry discovers the mirror, he walks through a door and finds the mirror on his right. It is the same when he takes Ron, played by Rupert Grint, to see it.

But when Dumbledore finds Harry gazing into the mirror, the door is no longer there. Instead, there is just a wall.

When the troll is scaring Hermione, played by Emma Watson, in the girls' toilets, there is only one line of cubicles, but he smashes the top half off twice.