Simon Yates retained the maglia rosa as Tom Dumoulin could only finish third in a Giro d'Italia stage 16 time trial which was won by Rohan Dennis.
Yates limited his losses on a day which was seen as pivotal in the general classification battle, time-trial specialist Dumoulin only able to reduce the Mitchelton-Scott rider's advantage to 56 seconds on the 34 kilometre course from Trento to Rovereto.
Coming into the stage, the race leader's explosive climbing had given him a margin of two minutes and 11 seconds over world time trial champion Dumoulin, who was unable to do significant damage at the start of the final week.
It was no secret that Yates is far less at home in time trials than he is in the mountains, but the Brit has given himself a golden opportunity to claim a maiden Grand Tour title in Rome this weekend after passing a major examination on Tuesday.
Australian Dennis put the hammer down to take his first Giro stage win in a time of 40 minutes ahead of Tony Martin.
BMC Racing's Dennis crossed the line 14 seconds quicker than Martin, with defending champion Dumoulin 22 seconds off the pace.
Chris Froome finished in fifth which was good enough to move up to fourth spot in the GC standings. He trails Yates by three minutes and 50 seconds behind third-placed Domenico Pozzovivo, who now sits over three minutes back from the leader having finished 33rd in the time trial.
Thibaut Pinot had a day to forget, slipping down to fifth place overall, finishing three minutes and 19 seconds off the pace of Dennis.
YATES PASSES STERN EXAMINATION
Yates said there was a danger he could blow up to undo the good work and end his title hopes given that time trials are not his forte.
But he knuckled down impressively to finish 22nd after coming off the ramp last, reaching the second intermediate in 30:44 and pressing on under the strain with so much at stake.
Dumoulin was 21 seconds up on Yates at the first check and stretched that to 48 at the second, which was 24km in.
The Dutchman threw everything at it in the closing stages, but it was not enough to take a stage win - which would have earned him a 10-second bonus - and Yates should sleep far more easily than he might have feared on Tuesday evening.
Dennis showed why he was one of the favourites to win the stage, reaching the second split six seconds ahead of Martin and keeping hold of his advantage.
Froome was sixth at the first split, but motored on in the latter stages of his run with an excellent recovery, keeping him firmly in the hunt for a podium finish.
1. Rohan Dennis (BMC Racing) 40:00
2. Tony Martin (Katusha Alpecin) +0.14
3. Tom Dumoulin (Team Sunweb) +0.22
4. Jos van Emden (Lotto NL-Jumbo) +0.27
5. Chris Froome (Team Sky) +0.35
1. Simon Yates (Mitchelton-Scott) 66:39:14
2. Tom Dumoulin (Team Sunweb) +56
3. Domenico Pozzovivo (Bahrain-Merida) +3:11
1. Elia Viviani (Quick-Step Floors) 237
2. Sam Bennett (Bora-Hansgrohe) 197
3. Simon Yates (Mitchelton-Scott)) 113
King of the Mountains
1. Simon Yates (Mitchelton-Scott) 91
2. Giulio Ciccone (Bardiani-CSF) 52
3. Esteban Chaves (Mitchelton-Scott) 47
A 155km ride from Riva del Garda to Iseo is not expected to see any change in the GC battle, with just a few climbs at the start and in the middle of a 17th stage which will give an opportunity to attackers. The Alps will follow later in the week.