Nowadays not all AGAs need a flue: the electric AGA just has a small oven vent pipe that runs horizontally to outside.
The latest Total Control and Dual Control AGAs can be specified either with the 'external vent' pipe and external fan box, or as 'room vented' not requiring any pipework from the cooker to outside.
Is this the black pipe off the top of the cooker?
No, the electric AGA oven vent pipe is a small (28mm diameter) copper pipe that exits the back of the Cooker just below worktop level and runs horizontally to the fan box which is mounted on the wall outside.
(NOTE: It's not recommended to terminate the pipe in to a chimney.)
There is a small flexible cable runs next to the pipe to the feed the fan box from the AGA (extra-low voltage, 24V DC maximum).
It can run up to about 4m of straight pipe, reducing in length to allow for any bends that may be needed (bends add resistance).
The pipe needs to gently fall to outside and cannot incorporate any dips or troughs (which would fill with condensate and block the pipe).
We can check the proposed route to outside when we come to carry out the home survey before your AGA is installed.
The AGA 7 Series, Total Control and Dual Control AGAs come as standard with 'room vented' ovens but can be specified (if the positioning of the cooker allows) with the external oven ventilation pipe system. (It's recommended to have an extractor fan above these to take the cooking smells to outside.)
Note: You can't convert a room vent Total Control AGA to external vent model (or vice-versa) but most Dual Control AGAs and the AGA 7 Series cookers can be swapped if it's practical to fit the system. (It's not straight-forward [or cheap!] - you have to pull the cooker forward to get to the connections and fit the kit.)
AGA 3 Series and AGA 60 have no pipe or flue to outside - these are 'room vent' only.