Chelsea boss Frank Lampard feels their modern day rivalry with Arsenal was sparked in 2004.
On that spring evening, Chelsea faced Arsenal in the second leg of a Champions League quarter-final at Highbury, with the aggregate score 1-1.
On the stroke of half-time it was 2-1 to Arsene Wenger's table-topping side but then Lampard equalised before Wayne Bridge snatched a winner late on to complete a historic victory - a first win against Arsenal since 1998.
"The evening was a turning point when we got that result because it gave us a huge amount of belief at that time," he told chelseafc.com.
"We had not managed to beat Arsenal in my first days at Chelsea because they were a really strong unit and they had been built up for quite a number of years under Arsene Wenger, and we were changing, we were young. That night gave us belief so it did push us on at that point."
He continued: "When I joined at Chelsea, Arsenal had the upper hand on us and had won league titles before I came here. As we managed to change that a lot, there was obviously clear rivalry, as you would expect with London teams anyway.
"I enjoyed that side of it, as long as it is controlled and carried out the right way, which I think it was for most of the time. I think that rivalry remains. My role now is different, I am not on the pitch, the players have to play with controlled passion because that is what a derby brings."
