There were 2 schools of thought on doing SRA's to 05. Some Watches had 2 Directors with each doing alternate one's as Talkdownman says and some had the first Dir sequencing to final and then at 6nm hand over to the 2nd for the full SRA as he would just have transferred the first to Twr at 2nm or more. This meant that each Dir only did 1 job i.e sequencing or SRA'ing rather than doing both at the same time, plus the Twr always knew who to ring if there was a problem or to give a landing clearance.
How could you ever explain to SRG nowadays "shooting the gap" with a departure from 10R cleared for take off (or at least told "Roll Now Take off clearance to follow") against tfc that still hadn't landed on 05!