What is the date of this drawing?
Who cares? It looks like a middle-school art student made it.
The OP, apparently.
The cars looks like mid-Eighties models, if that’s any help.
Your link has an email address; have you tried sending a question?
I looked for Dawes Gray on Wikipedia - no luck.
He’s the artist?
My quick research suggests that Dawes Gray is a woman, who went to Rochester Girl’s Grammar School, and was born about 1970. http://dawesgray.co.uk/about.html