Help!!

I have been asked to create a top-hat cake for a friend but have to travel some distance with this is my car.

Firstly how do I make it tall enough and stable enough?
Safest place to place in car?
Pictures and instructions please

Lilli

Every 3-4" of cake height stop, cardboard, and dowel just like a tiered cake but ice it all together in the end. Very stable and the pieces will be manageable. Safest place is the trunk or floorboards with non-skid.