A necessity: Eye make-up remover. I always wear eye make-up and, if I can't remove it properly at the end of the day, I feel all gungy. Soap and water is never enough.

A luxury: A good, thick escapist novel, but a well-written one. I hate bad writing.

A memento: I have a little gold Columbian figure which was given to me by a colleague when I was working in the US 20 years ago. It is in my purse wherever I go and is like an old friend.

If only: I would love a personalised collection of miniature toiletries. I always take too much as I'm worried about running out.

• Susan Greenfield is director of the Royal Institution. Her series Brain Story begins on BBC2 at 9pm on Tuesday July 18.