Manchester City and Chelsea have walked side by side through the wildly vacillating fortunes of football for more than four decades. Theirs is truly a history entwined.
Parallel episodes in the two clubs' histories can be traced back as far as the late 60s. With flower power in full swing, a vibrant and varied music scene in Manchester and London taking off, fashion and football came together for the first time, with City and Chelsea in the vanguard of the new cool.
In London, Hollywood siren Raquel Welch was pictured at Stamford Bridge cuddling up to superstar striker Peter Osgood, while further north Mike Summerbee and George Best were opening their fashion boutique Edwardia near King Street West. Footballers from the two clubs were at the forefront of the shift from baggy shorts and Brylcream to flashlights and glamour.
The late 60s also saw City and Chelsea in the spotlight when it came to trophy-winning, with both clubs scooping various domestic and European prizes. The Cup Winners Cup, won historically by both in 1970 and 1971 respectively, even featured a high-profile semi-final between the two clubs in 1971, with the dark blues edging past an injury-ravaged City side to reach (and win) the final against Real Madrid.
In the 70s the two clubs' fortunes again matched each other as a serious rot began to set in. From the swinging sixties, first Chelsea and then City hit the wall of doom and despondency. There were two memorable City hat-tricks around this time: with the Londoners wilting first, City hit them for six at Maine Road in November 1977, a devastating Dennis Tueart hat-trick setting them on their way. A season later, with great spaces appearing on the Stamford Bridge terraces, City won 4-1 in the sun, with a hat-trick from Ron Futcher sealing the victory. The return that season saw Chelsea gain revenge in desperate conditions, a by now ageing Osgood - without the close attention of Raquel Welch - grabbing one of the goals in a 3-2 win.
Chelsea would be relegated, followed three years later by their northern cousins.
The 80s saw real decline and - with both sides languishing in the second tier - more memorable games that proved to be significant milestones along the road to recovery. Jim Tolmie's cracking free kick at Stamford Bridge in 1983 saw City take the points, but, by the end of a torrid season, it was Chelsea, ahead of big guns Sheffield Wednesday and Newcastle, who went up. Four into three didn't go, so City remained rooted.
By the end of the decade both clubs had been promoted and had re-descended the ladder. In 1989, with promotion hanging between them, a rain-drenched cliffhanger ended 3-2 to the visitors to Maine Road. Even then, with football's rot well and truly setting in, 42,000 produced the kind of atmosphere seldom heard at grounds these days.
The third parallel has come about in the last 20 years. With investment has come an elevation to football's elite performers. Chelsea arrived first, bankrolled by Mathew Harding, then later Roman Abramovic, and the titles soon followed. City's story again mirrored their London rivals and the outcome has been largely similar.
The road has been long and winding, pocked with pot holes and scarred with pitfalls. There has been glamour, star players and continental adventures balanced out by relegations, chaos and decay. But football also reinvents and today we see two clubs in the finest of good health.
With a nod to the likes of Osgood and Summerbee, Tueart and Ray Wilkins, Kerry Dixon and Paul Stewart, we await the next instalment of a battle of two shades of blue that has never been anything less than completely invigorating.