browndog:Marie: you are not blind dense or stupid....... for some strange reason Canon forgot to add a PC socket to the 400d. You can use a bog standard hotshoe adapter to fire the flash.
hope this helps
David
Thanks for that David,
Glad I'm not going senile before my time! Looks like it'll have to be the adaptor then. Love this site, always gets a question asnwered!
Take Gentle Care....
Marie