Chaser - just to clarify (same sheet of music etc) the radar separation standard wes 3nm between the centre of the two radar returns, but returns never to touch.
With two SSR Returns (symbols) the standard was 5nm, or a mix of primary and SSR 5nm (or it was in my day pre TAAATS/ADATS - I last controlled live in 1992).
Is it now 3nm between centre of the (system generated) symbols? (noting that in some cases, the position of the aircraft "symbol" is a system corrected display given that the aircraft could be detected by several radars in some locations and the "system" generates an "agreed" position - for want of a better word?)