Nobody has yet pointed out that speed limits generally were set at the
nearest 10 mph lower than the 85th percentile (approx from memory) of
all road traffic on a stretch of road (blanket 30 mph zones excepted)
in the 1960s. Therefore, "exceeding" a posted speed limit just means
that you are driving faster than the 85th percentile - not an offence
if you are driving sensibly.

Since the 1960s car control has improved tremendously from power
steering through ABS brakes, yet the Highway Code still has the
stopping (thinking/braking) distances of old. I would like to see
these distances recast for modern cars with two tables, one for dry
conditions and one for wet. Modern downward tinkering of speed limits
is practically all about anti-car, not common sense, cf ever
increasing swathes of 20 mph zones, etc.

Speed cameras are a danger (except at real accident black spots) as it
is a reflex action to brake when you see one on a road not traveled
before, and you lose concentration checking that you are 'safe'.
There is also the huge cost to the economy of braking/accelerating and
wear and tear on the brakes at these points and at speed cameras in
general. As the tolerances for speed cameras are not advertised, then
it is foolish to risk your license by driving past at any mph above
the posted limit.