Tunstall dropped down from the Memorial .
Tunstall added to the 23 second lead at the summit with a strong run around the reservoir and the 4k downhill section , increasing the margin to 52 seconds at the finish .
Dropping down from the Memorial , Tunstall added to the 23 second lead at the summit with a strong run around the reservoir and the 4k downhill section , increasing the margin to 52 seconds at the finish .