Had my cruise control and camera confirmed I was doing 31 mph and 45mpg.
Had a stack of cars sitting on my bumper trying to get me to speed up in 30mph neighbourhoods.
Slowing down or driving at the speed limit can be safer and could increase your mpg in some cars.

Just ignore the prats speeding behind you.
If it’s emergency they can overtake or they can call the police.

Meanwhile back on fuel economy measures…

A good rule of thumb is that braking wastes energy so try to drive with as much anticipation and little use of the brakes as is safely possible. This results in less acceleration between junctions and earlier lifting off the accelerator when approaching hazards. Saves fuel, passenger stress and mechanical wear.

If you’re impatient, that’s your problem – you can wait for a straight or wait for me to pull over. Which I will, cos I’m considerate.

Then it’s true – you’re…… the one.

If it’s emergency they can overtake or they can call the police.

I generally assume that if the person up my backside’s journey was that important s/he’d have flashing blue lights mounted on their vehicle.