406 sump plug

I have decided to change the oil on my 2.0 406 T-reg at 50,000 miles as next service will be due at 60,000. Have bought oil and filter, removed splash guard from under engine. Filter is accessible ok, but cannot see sump plug. From previous cars I was expecting a large nut (and copper washer) at bottom of sump which would be undone using a spanner held horizontally, but I can't see anything obvious. A silly question, but does anyone know where the sump plug is? Maybe it's just my eyesight is going!