I don't think I've ever known calm to gale force conditions happen so quickly.

If you use your imagination it looks a bit like the eye of a hurricane
passing over the SW peninsula on satellite imagery. I guess the rapid
increase in wind speed was from the passage of the eye as the low centre
tracked across you to the rain and strong winds on the back side of the
low, possibly enhanced by a sting jet.

I'm curious as to how much more potent (if at all) this low would have
been had it developed in the winter with more baroclinic energy to feed off.

Maybe this? http://www.sennen-cove.com/10march08.htm

It occured to me that the pressure gradient only went some way to explaining the wind strength and it's incredibly rapid onset.

The rapid fall in temperature was also notable, in Penzance from around 10C to 5.7C in 30 minutes.

Even away from the north coast, the exposed parts of west Cornwall saw 70mph.
Culdrose reported a mean speed of 46mph, gusts to 67mph @ 19:00, the peak was slightly earlier. Sevenstones was reporting mean speeds of 7mph @ 15:00, 58mph @ 16:00, so a F10 over the sea. The strongest gust I've seen on land was a 75mph at St. Ives.

Graham
Penzance