Originally Posted by
Swiss Tony
Just to throw an idea in, how about Hampton Court? Or Kew Gardens?
For me the risk is that the 1hr 15 min drive could easily double in duration if you run into some kind of problem like an accident on the M3.
Also figure additional time for collecting and returning a rental at LHR. You must take a shuttle to/from the terminal to the rental car lots on the airport perimeter; then there is refuelling before return (unless you enjoy paying US$15/gallon for Hertz to do it). All this could add at least 45 mins each way.
PS: +1 on Hampton Court/Kew Gardens with a relaxed lunch/dinner on the river at Richmond