Thank you, everyone, for your input. Some interesting intrigue and speculation from all of us but now I know more about the situation.
Today was my first day at the caterer's kitchen (the people catering for the wedding), where I am working on the cake. It appears that the chef is helping out the bride with this because a private cake decorator went out of business, leaving the bride in the lurch. She wants a simple groom's cake, featuring the edible image of the groom's car. She stressed simple and not at all feminine - no fuss. This is the cake she wants and I will do the best I can to please her.
If I continue to do this into the future then I would want to collaborate with the clients on designing a cake. However, in this situation, it just wasn't feasible and it appears that the bride is happy and easy-going.
Thank you all again.
All the best,