Combined driving also known as Horse Driving Trials is an equestrian sport involving carriage driving. The sport has three phases, and is most similar to the mounted equestrian sport of eventing. It is one of the seven international equestrian sport horse disciplines recognised by the FEI (International Equestrian Federation).
The sport is carried out at different levels in the UK, with 100's of drivers competing at national level.

HRH Prince Phillip is a patron of the sport and a keen driver and until recently also a competitor.

There are 10 events at national level in each season and these generally run between April and September and are held at some of the most prestigious country estates in the UK including Sandringham and Windsor.

Each event lasts for 3 days (Friday, Saturday & Sunday) with a phase on each day. Each event will generally have up to 100 drivers competing across the different classes.

The competition will start with Dressage where the judges firstly grade on presentation and general condition of the horses, tack, carriage and the presentation of the driver and grooms.

The Dressage test itself is judged by 3-5 judges and dressage movements may include circles, figures of eight, crossing the diagonal and all paces - walk, working trot, collected trot, extended trot, canter, a halt, and a rein back. Multiple horses are judged on ability to move in harmony and ideally will have similar conformation, action, and movement. Horses are to remain on the bit throughout the test, maintaining impulsion, elasticity, rhythm, and forward movement. The goal is to make the test look effortless, and an obedient and responsive horse is essential for a good dressage test.

Day two has all the excitement of the Marathon which is the most thrilling phase to watch, and often draws the largest crowds. The marathon tests the fitness and stamina of the horses, as well as the driver's knowledge of pace, over a 10-22 km course, divided into 3 or 5 sections. The Marathon has obstacles or "hazards" throughout the course to test the speed and agility of the horses, and the driving ability of the whip. Obstacles may include water, tight twists through trees or man-made obstacles, steep hills, or fences and pens. Drivers are scored on how quickly they can negotiate the obstacle, and must find the fastest route through each.