Pompey picked up a record-equalling sixth clean sheet on the way to a 1-0 success over Sheffield United today.
But the Blues had to withstand a second-half battering from the strugglers to equal the post-war league record for shut outs.
Steve Cotterill’s men also set the new benchmark for clean sheets by a Championship side this season, as Hermann Hreidarsson grabbed the only goal of the game.
That ensured Pompey kept up their unlikely charge towards the play-offs. They are now in 11th place - seven points off the top six.
The Blues were good value for their first-half lead as Hreidarsson slammed in a loose ball from a corner after 24 minutes.
But the longer the game went on the more nervous they became, as Sheffield United belied their lowly position.
The home side’s new-found resilience saw them hold on, though, to get a great win.
It’s now 596 minutes since Ashdown has conceded, with the run equalling Peter Mellor’s six game league record back in 1978-79.