Arsene Wenger memorably declared Dein's departure from the Gunners in 2007 as a "sad, sad day for the club."
The North Londoners have not won a league title since with Arsenal fans often citing Dein's knowledge, guidance and passion as crucial missing factors.
But it seems Dein's knowledge stretched beyond North London.
At the time, under the ownership of the doomed Icelandic consortium and chairman Eggert Magnusson, West Ham were exploring the possibility of a future move to the Olympic Stadium, which had yet to be built.
While it was actually owners David Sullivan and David Gold who eventually brokered the move to the 60,000 seater stadium which takes place this summer, Dein's remarks were telling.
'It frightens him to death'
"We tried to do a deal with London 2012 but the real problem was we did not have enough money," Brown said back in 2006, as reported by the Independent.
"I think the new owners (the Icelandic consortium) are keen on the idea and there is a real possibility they will go down this path.
"It could be a fantastic development for east London.
"David Dein of Arsenal tells me the prospect of West Ham in the Olympic Stadium frightens him to death."
Dein's fears being realised?
It is clear to see why passionate Arsenal fan Dein was so fearful.
The West Ham support has always been recognised as one of the finest and most loyal in the country.
The Hammers have taken huge strides forward this season under Slaven Bilic with stars like Dimitri Payet and Manuel Lanzini rediscovering the 'West Ham way'.
Bilic's side are serious contenders for the Champions League places and have their sights set on a fitting FA Cup win for the final season at their beloved Boleyn Ground home of 112 years.
Olympic leap for Hammers
And all this before the club moves into its new 60,000 home this summer, the capacity of which was increased after the club sold out season tickets five months early.
That's the same as the Emirates and even without the increased revenue the move will bring, West Ham are only five points off the third-placed Gunners who they could leapfrog - depending on results - when the pair face each other at Upton Park next week.
If the prospect of the Hammers moving to the Olympic Stadium frightened Dein, then how must he feel about the very real possibility of the ground's capacity being raised further still to 66,000 in the 2017/18 season, a fact recently confirmed by co-owner Gold?