There is still work to be done if the Three Lions are to book a place at Brazil 2014, but they can now rest a little easier heading into Tuesday's clash with Poland at Wembley.
England endured a frustrating first half in which they created little in the final third, but broke the deadlock three minutes after the interval when Wayne Rooney bundled home from close range after a Danny Welbeck shot was parried into his path.
A moment to forget for Branko Boskovic saw the home side double their lead just past the hour mark, as he put through his own net, but Montenegro threatened to set up a nervy finish when an instinctive prod from Dejan Damjanovic hauled them back into the tie.
Townsend was, however, to ease the tension hanging around the home of English football on 78 minutes with a spectacular swerving effort from 25 yards out which put the gloss on an impressive senior international bow for the Tottenham midfielder.
A fourth was to follow in stoppage-time, with Daniel Sturridge stepping up to calmly stroke home from the penalty spot after being felled inside the box by Ivan Kecojevic.
Welbeck went close on a couple of occasions during a right opening 45 minutes, including one effort that was deflected to leave Vukasin Poleksic stranded.
But it was his Manchester United team-mate Rooney who came closest to breaking an increasingly tense deadlock.
Townsend was the architect, smashing a shot at goal Poleksic could only parry into his path.
The angle was tight. However, a player of Rooney's quality would expect to do far better than clip the outside of a post given the closeness of the contest.
As the half-time break brought news of a 1-0 win for Ukraine in Kharkiv that meant anything other than victory would almost certainly condemn England to the hazardous play-offs at best, a few nerves could have been forgiven.
None were showing though as within three minutes of the restart England had the goal they craved.
It was no surprise Townsend was heavily involved. He charged down the wing at speed before pulling a cross back that was flicked into Welbeck's path. His shot did not beat Poleksic but it was hit with enough power to prevent the Montenegro keeper from holding it.
Rooney stuck out a leg, brought the ball under control and from a central position calmly slotted it in.
The sense of relief was palpable, matched almost by stunned amazement at the manner of England's second.
Sturridge's back-heel released Welbeck, whose cross was dangerous only for Boskovic, who, from 12 yards, somehow found the bottom corner when he was attempting to clear.
It was the type of good fortune absent when Kyle Walker picked up a costly booking which rules him out of the Poland game, but England benefited from as Joe Hart saved from Damjanovic and Stevan Jovetic rattled the bar from long range.
Those misses, either side of that bizarre own-goal, seemed to sap the will from visiting legs.
Steven Gerrard and Welbeck both failed to make the game safe but it seemed only a matter of time before someone did.
Instead, Damjanovic got his foot to Fatos Beciraj's shot to set up a nervous final 19 minutes.
For the first time Hodgson looked a little worried as he sat on the bench, chewing at his nails.
Townsend was not watching though. He just picked up the ball and ran straight through the heart of Montenegro's defence before producing a brilliant finish.
There was still time for an injury-time penalty, converted by Sturridge after he had been fouled by Kecojevic, but it was academic.
Goal difference does not matter now. Beat Poland and England are through. Fail and they head into the play-offs.
|0||1st Half Goals||0|
|12||Shots on Target||2|
|10||Shots off Target||6|
|62.4||1st Half Poss.||37.6|
|58.5||2nd Half Poss.||41.5|