Historic rallying is true and highly-competitive rallying over the same stages as modern rally cars.  The only difference is that a "historic" rally car has to be of a type used before 1968.  "Period modifications" are allowed, but the driver has to prove a modification really was in use at that time if challenged. 

There's a further sub-division for pre-1960 cars, which run for separate awards.  The reasoning there is that these were historically significant dates.  From 1960 the Mini came onto the scene in modified form, then in 1968 the big Escorts began to appear.  That doesn't mean that Escorts are altogether exluded, as there is another category with the rather clumsy title "post-historic", and that covers cars up to and including 1974.

And if it's beginning to sound complicated, that's only the start.  Some events allow later cars under the heading "Classics" and in all categories there are different regulations depending whether you're talking about (British) Motor Sports Association, or (International) FIA rules.  Naturally there are various classes based on engine capacity, and Porsche 911's usually run in their own class, because they're unfairly quick, specially on asphalt.

(see "Links" for more info -- this site's mainly about pictures!)
 

click the link for a page or two of pictures of each event

round 1: Ypres Historic & Classic Rally 2001
round 2: Harry Flatters Historic Rally 2001
round 3: Astra Stages Historic Rally 200l
round 4: Premier Rally 2001
round 5: Bulldog Rally 2001

click the link for a page or two of pictures of each event

round 1: Robin Hood Stages
round 2: Vauxhall Astra Stages
round 3: Tour of Cornwall
round 4: Millbrook Stages
round 5: Ypres Historic & Classic Rally
round 6: Harry Flatters Stages
round 7: Trackrod Historic Cup
round 8: Bulldog Rally
 

click the link for a page or two of pictures of each event

Astra
Scottish
 

page 1  assorted pictures
page 2  assorted pictures
 

the Historic Rally Car Register organises the MSA British Historic Rally Championship
HERO, the Historic Endurance Rallying Organisation, organises long distance rallies
the MSA, formerly the RAC Motor Sports Organisation, oversees and regulates motorsport in the UK