Which lane coming out of South Mimms services?

Which lane do people use when coming out of South Mimms, Bignells corner services when heading to the A1 southbound? There are two lanes out of the services and as the A1 is effectively to the left I have always used the left lane and cut across to the first lane for the A1. But the other day I had someone in the right lane doing their nut at me for doing that. Never had an issue before but it got me thinking what is the appropriate lane as it involves cutting across the two lanes that head to the M25. What lane do people consider correct?

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