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I agree with @Dilly. The icon appeared in V11 and it replaced the old NAVIGATE ON AUTOPILOT button. It only seems to appear if the route includes certain types of dual carriageway or motorway.
Yes, It is Navigate on Autopilot. It will make lane recommendations based on traffic and junctions and it can handle some motorway junctions but not all of them.
I know it can do M4 West to M25 Clockwise, M3 North to M25 East, M25 Clockwise to M3 South, and if you have the nerve it JUST does M4 West to M25 Anticlockwise