Mervyn King celebrates after coming back from the brink to defeat Raymond Smith at the PDC World Darts Championship ©Getty Images

Mervyn King and Luke Humphries both won seven-set thrillers as the fourth round of the Professional Darts Corporation World Championship continued at Alexandra Palace in London.

In the first match of the afternoon session, England’s Mervyn King overturned 2-0 and 3-1 set deficits to triumph 4-3 at the expense of Australian Raymond Smith.

Smith edged a tight first set by three legs to two but won sets two and four without dropping a leg to put himself a set away from victory.

The 21st seed King stormed back winning the next three sets for the loss of just a single leg as he completed a dramatic comeback.

The other match in the session that went the distance saw England’s Luke Humphries, the 19th seed, beat compatriot Chris Dobey, seeded 30th, 4-3.

Dobey took the first set in a deciding leg and won the second without dropping a leg to open up a 2-0 lead.

Dobey then won the fourth set by three legs to two to put himself a set away from victory before Humphries fought back in this back and forth match, winning the next two sets 3-1 to set up a decider.

With a player required to win a deciding set by two clear legs, extra legs were required with Humphries eventually prevailing in a tense and thrilling encounter by five legs to three to secure his quarter-final spot.

The afternoon’s other match saw England’s Callan Rydz come from a set down to defeat Scotland’s Alan Soutar 4-1.

Soutar won the first set by three legs to one but from that point Rydz ran away with proceedings, winning the next four sets for the loss of just a single leg.