The message
from John Rumm contains these words:

Many modern cars can pull over 0.6g in a corner, they can usually stop
much better than that.

The handbooks for the 60s/70s Lotus Elan and Plus 2 contain the following:

"capable of exceeding .9g retardation"
and
"capable of exceeding .8g lateral side load".

Were they really 40 years in advance of their time? :-)

Most bods who tried found they could stop in the dry within 55m
including thinking time. If you accept the highway code thinking
distance at 70mph (31m/sec) being 21m, then that only leaves 32m to
actually stop in.

In g terms that gives us:

v^2 = u^2 - 2as

a = (v^2 - u^2) / -2s

a = (0 - 31^2) / -64

15 m/sec^2 or about 1.5g

(It maybe that their thinking time in these tests was less than in real
life because they were anticipating the event).

My money is on them ignoring thinking time completely.

--
Roger Chapman