There was once a time when Manchester United were the undoubted kings of Manchester - but then the noisy neighbours came along and rattled plenty of cages.
One former Manchester United player who rarely had to deal with such a competitive Manchester City side was Gary Neville.
Neville, now a Sky pundit and coach within the England setup, played for United in an era in which they dominated - with only Arsenal and Chelsea sustained threats during his 20 years with the Red Devils.
But this morning he inadvertently, in his own words, started ‘world war three’ on Twitter between rival fans of the Manchester clubs.
It came as he revealed he and a Manchester City legend had recently put together a combined Manchester XI from the Premier League era.
It was he and Mike Summerbee, who played over 400 games for City between 1965 and 1975 who put together the team - and he only found place for three City players in his XI.
Vincent Kompany, Pablo Zabaleta and Sergio Aguero made it - and in all honesty he could not have been expected to put many more in.
He left himself out for Zabaleta and struggled over the inclusion of Yaya Toure - but overall it seems a fair assessment of how you would combine the Manchester clubs from the Premier League era.
Check out the Tweets that gave Neville a headache this morning:
Was at a dinner with Mike summerbee 2 weeks ago and we had to wrestle over a combined MU/MC eleven during PL era! What would yours be?— Gary Neville (@GNev2) March 23, 2014
It think it ended up as this! Sch. Zab / Kom/ Stam/ Irwin Ron / Keane / Scholes / Giggs Roo. Aguero— Gary Neville (@GNev2) March 23, 2014
Remember it's not mine it was mine and Mike's! Negotiation / Compromise etc etc!! Haha— Gary Neville (@GNev2) March 23, 2014
I argued for myself to be in but he was adamant !! Hahaha..— Gary Neville (@GNev2) March 23, 2014
Just started world war 3 on a pleasant Sunday! Manchester Derby this morning! United v City U'12's! Score updates to follow!— Gary Neville (@GNev2) March 23, 2014
What isn't a debate amongst City and United fans on replies only 4 city players could ever be considered! Zab/ Kom/ Yaya/ Aguero! Rest Utd!— Gary Neville (@GNev2) March 23, 2014