Vincent Kompany's powerful header sealed a 1-0 win for Manchester City over title rivals Manchester United on Monday to put Roberto Mancini's side within two victories of Premier League glory.
The Belgian defender rose unmarked just before halftime at the Etihad Stadium to settle a compelling and frantic derby that lacked quality but more than made up for that in tension.
United could not respond as City moved above their neighbours on goal difference with a match at Newcastle United and a home game with strugglers Queen Park Rangers to come.
Both sides have 83 points, with City having a superior goal difference of eight, and the momentum is now with Roberto Mancini's side who have clawed back an eight-point deficit since Easter to move within sight of their first English title since 1968.
A crackling atmosphere greeted the players as the sun set in Manchester and it was Alex Ferguson's experienced title winners who began with real urgency.
There were clearly some nerves in the home ranks, both on and off the field, and United threatened in the opening minutes when Ryan Giggs was allowed too much time to cross into the box and, as City struggled to clear, Michael Carrick prodded wide.
With Diego Maradona watching from the stands it was City's South Americans who began to warm to the task, along with Spaniard David Silva who orchestrated City's attack.
Argentine Carlos Tevez got free on the right but his cross was well cleared and then compatriot Sergio Aguero sliced a shot high and wide when well placed.
Kompany was enjoying a good old-fashioned scrap with Wayne Rooney and the City captain was booked for one rumbustious tackle on the England striker who became marginalised as the half wore on.
United found themselves pinned back as City began to hog possession and Aguero again failed to make the most of another half chance that came his way.
The visitors would have been happy to hear the halftime whistle on level terms but Kompany, sent off when the sides met in the FA Cup this season, chose the perfect time to score.
When Silva slung in a corner the Belgian evaded the attention of marker Chris Smalling and thumped a header past the helpless David de Gea.
United could never really find any attacking rhythm after the break as City erected a sky blue wall to deny United's forwards players any quality service.
With the clock ticking and the visitors becoming desperate tempers flared in the technical area with Mancini and Ferguson involved in a heated exchange.
City's Yaya Toure almost gave his side breathing space with a shot that whistled wide.
Ferguson threw on Danny Welbeck and Ashley Young to bolster United's attack but City held firm to spark a deafening rendition of club anthem Blue Moon.