The visual giveaways (other than size) that an aircraft is a Warwick are:
- (due to the longer fuselage) the propellers are behind the cockpit (on the Wellington, they are level with the cockpit)
- the engine nacelles are all below the wing (on the Wellington, they are both above and below the wing)
- the Warwick has a mid-upper turret and
- (sometimes) the Warwick has a dorsal extension ahead of the vertical stabiliser.
Structurally, the Warwick fuselage was a Wellington fuselage with an extra section just ahead of the wings, and the wing structure was different (the main difference being that there was no gap in the wing structure for the engine nacelle, as there was on the Wellington).
Hope that is helpful.
Regards,
Iain.