was forced to overrule final referee Desislava Bozhilova after she made what could have been a crucial mistake in the match. Williams was down 3-1 to and facing a pivotal moment in the fourth frame after snookering himself.

The 50-year-old potted a long red into the bottom-right corner, drawing huge applause from the crowd in what had been a difficult start for the veteran. However, he accidentally nudged the black ball into the pack of reds and did not have a shot at a colour.

Unfortunately for Williams, the cue ball fell to the other side of the pack to the red and he was forced to play back into them after an impressive opening effort.

Cueing over the table, Williams nominated the black ball as his intended target, planning to come off the bottom cushion and tap it safe into the pack. However, Bozhilova misheard him and incorrectly declared the more difficult yellow on its spot as his intention.

But Williams caught the error just in time and while peering over the cue ball, ready to hit it, said: "Black ball?!"

The Crucible crowd erupted into laughter as the referee then re-declared the black as the intended target, which Williams successfully played. As he manoeuvred back to his seat Bozhilova could be seen with an awkward grin on her face, all in good nature, but thankful that the Welshman noticed her miscall.

The Bulgarian official is , and the first woman to referee the final of each Triple Crown event - adding to her and finals.

She has already officiated a World Championship semi-final and is considered one of the sport's top referees, having spent 13 years on the World Tour as a ref.

"I am really excited, it was an amazing feeling when I was given the news," she said after becoming the second female final ref after Michaela Tabb in 2009 and 2012. "It is what I have worked towards for many years, it has been my dream. It will be different to any other final because of the atmosphere at the Crucible.

"Since I started working in snooker, I have learned everything from the more experienced referees. They give advice and tell us how to improve. There is a lot of teamwork, and we support each other."

Unfortunately for Williams, he was unable to take the fifth frame to the first-ever final between two left-handed snooker players.