Everything I read say that Shaking a Martini is not the way to go. I took chemistry a couple of times (I mean the same course a couple of times. I love the Fleming building, what a coincidence).
So I understand this is all chemistry. So, Shaken or Stirred.
Purists argue you have to stir so you don’t break up the ice and water it down. And if you’re using legit gin, think Bombay sapphire and up quality wise, I’d agree. Below that I’d let the water mellow out the cheap booze.