CALNE shrugged off the loss of the suspended Jordan Roberts and Kyle Ridley to storm to a comfortable away victory.
The Lilywhites turned in an assured performance and took the lead after 13 minutes as Portishead failed to deal with a corner and Lee Stevens fired home.
Three minutes later, Calne doubled their lead as a long ball from skipper Dan Lardner found Levi Cox who held his nerve to fire home the second.
Neither side held sway in the second half, although Tyler Sibbeck went close in the 73rd minute, his effort hitting the side-netting.
But Nathan Phillimore rounded off the match as he held off defenders to fire home the third.
MORE FOOTBALL REPORTS & REACTION IN THURSDAY'S GAZETTE & HERALD
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here