The Leicester potter took the seventh frame in the best-of-17 semi-final with the landmark break, which required a series of brilliant shots on the colours to bag him a £55,000 cheque plus another £4k for the highest break.
The 15 reds and blacks were picked off with minimal fuss, and yellow and green followed.
With brown and blue close together, though, an excellent shot was required to pot the former and run round the table off three cushions for position on the latter.
Stretching for the pink, he went through his full range of cue extensions and grimaced to the crowd and although he knocked the ball securely in, he left the cue-ball tight on the top cushion.
After again playing to the galleries with a mock scream, he settled himself to drop a dead-weight black into the centre pocket.
Selby pumped his fist, clasped hands with Walden in celebration and received a handshake from referee Paul Collier as a packed house at York’s Barbican Centre roared their approval.
Selby took the next frame as well, with the aid of a 53 break, on his way to a 6-2 lead at the end of the afternoon session.
The ‘Jester from Leicester’ took the next two frames to move within one of the final, before Walden battled back bravely to keep the match alive with a three-frame streak.
But Selby was not to be denied and won the 14th frame to earn a place in the final on Sunday against Australian Neil Robertson.