Spiral helps Saw horror franchise surpass $1bn milestone

The horror movie franchise Saw has now earned more than $1bn (£706m) in global ticket sales, following the release of the ninth instalment, Spiral.

It earned $4.5m (£3.1m) in the US and $2.67m (£1.8m) overseas at the weekend.

Starring Chris Rock and Samuel L Jackson, the newest film in the series follows the police hunt for a copycat inspired by the legacy of the "jigsaw killer" who set traps for his victims.

Saw debuted in 2004, with seven annual releases, before a revival in 2017.

Created by James Wan and Leigh Whannell, who also feature as executive producers on Spiral, the series was named the most successful horror movie series in film history by Guinness World Records in 2010.

The original Saw earned a massive $103m (£72m) worldwide from a $1.2m (£847,000) budget. It was advertised with the witty tag line: "Do you dare see Saw?"

Since then, every instalment with the exception of 2009's Saw VI crossed the $100m (£70m) barrier globally, while keeping production budgets below $20m (£14m). Saw III remains the highest-grossing entry, taking in $164m (£115m) worldwide.

Spiral has so far made $15.8m (£11m) in the US and $6.7m (£4.7m) internationally since its 14 May release, building a global haul of $22.5 (15.8m) million according to Box Office Mojo.

This means it has become the first Saw movie to top the US domestic weekend box office in a non-opening weekend.

So what's the secret of its lasting, if gruesome appeal?

"The popularity of Saw is intriguing," Robert McLaughlin, film distribution expert at Birmingham City University, told BBC News.

"It might be that fans of the movie want to tap into the old-school horror franchise model from the heyday of the 1980s and 1990s, when you could expect the return of Freddy on an annual basis.