Ben Brereton's smart finish – his first at Ewood Park this season – deservedly put the hosts ahead just after the break, but QPR hit back from the penalty spot through Lyndon Dykes.

It was hard to tell which way the game would go at that point, but Armstrong's composed 73rd-minute finish put the hosts ahead and he tapped in his 11th league goal of the season deep into stoppage time to secure the points and become the Sky Bet Championship's top scorer outright.

Blackburn are up to 12th after the result which ended QPR's two-game winning run.

Tony Mowbray welcomed back goalkeeper Thomas Kaminski and Armstrong, while the R's were without Bright Osayi-Samuel so Dominic Ball came in.

The hosts dominated the first half but Seny Dieng kept them at bay. He denied Scott Wharton a goal on his first Championship start since August 2016 on the half hour with the best of the lot, flinging himself to his left to flick the defender's downward header around the post.

He then thwarted Armstrong twice in quick succession, first by diving to his left to palm away after the striker had created space, and then by standing tall to repel his fierce effort.

The hosts were fortunate not to be behind just after the restart, though, as Ilias Chair's low cross found the onrushing Todd Kane at the far post and he hammered a shot that clattered the outside of a post.

But Blackburn got the goal they deserved in the 50th minute when John Buckley's cross was headed across the box by Darragh Lenihan towards Brereton who did well to adjust before firing a left-foot shot beyond Dieng.

The visitors were back in it from the spot in the 61st minute. Kaminski initially clawed away Yoann Barbet's far-post header, although the R's thought it had crossed the line, but in the ensuing panic to clear, the goalkeeper was adjudged to have fouled Rob Dickie.

And Dykes duly stepped up to blast the ball into the right corner.

Kaminski brilliantly tipped Chris Willock's shot over shortly afterwards and Rovers made it count 17 minutes from time when Harvey Elliott played Armstrong in and he clinically tucked the ball beyond Dieng.

Willock curled just wide as the game wore on but with QPR pushing forward, Armstrong made the points safe in time added on by surging clear and though the excellent Dieng saved his initial effort, the striker tapped home the rebound.