How do I get Alt-F2 to bring up the Run dialog box?

Are you referring to KRunner or something inbuilt provided by Compiz?

Sorry. My foolishness.

My keyboard recently packed up and so I am using an old multimedia keyboard. The keyboard has functions allocated to the function keys if a button called "Office Lock" is on (eg F2 = New). By default it starts on so it has been overiding the functionality.