The two matches involving Harlequins, Saracens, London Irish and Wasps - should they succeed in avoiding relegation from the Aviva Premiership - will attract a crowd in the region of 75,000.
In confirming the September 1 event, Premiership Rugby stated: "For the first time this season each club will be given a specific area of the ground for its supporters".
Premiership Rugby say the intention was to ensure each club's season ticket holders can sit together.
But it was interpreted by many supporters as the introduction of crowd segregation, an alien concept in rugby and it prompted an angry reaction.
Premiership Rugby were forced to issue a follow-up statement clarifying that supporters are encouraged to sit anywhere in the ground.
A spokesman for the Premiership clubs' umbrella body said: "There is absolutely no segregation at the London double header on September 1.
"Through Ticketmaster we have identified where club season ticket and friends and family allocations will be located, allowing fans to make their seat choices accordingly.
"We value the London double header, which brings together four teams and would encourage neutral fans to get behind a team for the day which makes for a great atmosphere within the stadium."
Should Wasps fail in their bid to avoid relegation, their place in the double header would be taken by another club.
The Premiership fixtures will be confirmed in early July.
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