Bernhard Langer threw away a two-shot lead on the final hole of the Senior Open and had to settle for a play-off with American Mark Wiebe.
The pair finished on nine under and two play-off holes could not separate them before darkness fell at Royal Birkdale.
They will resume their battle at 08:00 BST on Monday.
Langer, 55, looked on course for his second Senior Open title but found the bunker on the 18th hole and took a six to finish with a level-par 70.
Rain and lightning caused play in the final round to twice be suspended.
Langer held a three-shot lead heading into the final day, and looked to have secured the title with another solid round.
Wiebe, who shared the lead with Langer after the second day, carded a four-under-par 66 on Sunday which looked good enough for outright second until Langer's meltdown on the 18th.
America's Corey Pavin, Peter Senior of Australia and South Africa's David Frost tied for third at six under par.