I've read in several magainzes/books that Kate Winslet was Ian Callum's inspiration for the XK.

Here's a link to Jay Leno and Kate Winslet discussing the XK back in 2006:

 

Funny. Curious as she pronounced it "Jag-war" (at 2:30) being from the UK and all.

 

This is something I didn't know. I wonder if Jag ever gave her an XK for it.

 

I had to google this out of curiosity, and one of the links I got was to a Lexus forum discussing the interview and Ian Callum's confirmation of it. Was funny to read some of the posts by Lexus folk (of all people) panning the then brand new XK's looks.