Classic trials, or colloquially mud plugging, is one of the oldest forms of rallying or off-road motor sports, dating from the beginning of the 20th century.
All three Motor Cycling Club long distance trials in the UK – the Land's End, the Exeter and the Edinburgh – date from that time, and are still held today.
As vehicles became more reliable, the events became easier and the concept of observed non-stop sections was introduced.
On these, the car or motorcycle is stopped at the foot of a hill and has to make a non-stop ascent.
On a classic trial today, there will typically be around fifteen of such "observed sections", mixed with between 40 and 400 miles of road course.