Thule Cycle Carrier. I have had this for about 10 years, but they still make them, or at least something similar. This version carries three bikes and attaches to a tow bar. It has survived multiple trips to Scotland, Ireland and other parts of the UK. The bikes are attached by straps through the wheels and down-tube. Initially I was a bit worried about how safe/stable the bikes would be. However, I have never had any problems with a strap working loose, or a bike falling off in many thousands of miles!
You can tilt part of the carrier backwards, giving access to tailgate/boot, etc. Also Thule carry a range of spare parts, so if you break something it's easily replaceable.
They are quite expensive, but spread over 10 years it works out much less expensive than other carriers which don't last as long. Also as long as you have a two bar, it will fit any vehicle, unlike many other cycle carriers.