Thanks for the pointers, I had not seen the transporter. I have now solved the Duke's murder but am mowhere nearer finding the Dwarven Ambassador unless he is in the castle perhaps?
I am already a member of the thieve's guild and have basic pickpocketing skills (level 1) and lock picks 5 (as mentioned before) but I am not sure where this dagger actually is? Somewhere in the warren under the Ducal Inn I suppose...
Anyway - thanks for the help. If there is anything else I am missing I am sure someone will tell me

R G Bargy