Chalky seas and Colliding Continents


The chalk that makes up Portsdown Hill was laid down between 100 and 65 million years ago at the bottom of a deep tropical sea. Chalk is made from the compressed skeletons of countless millions of marine algae called coccospheres. The same layer reappears to the north where it forms the South Downs, and again to the south where it forms the chalk outcrops on the Isle of Wight. It is overlain by more recent deposits such as Reading Beds and London Clay.
A combination of movements in the earth's crust caused the hill to be pushed up about 20 million years ago, following the lines of weakness of much deeper ancient faults. These faults may still cause occasional earth tremors today.

Geology signboard

A more comprehensive description is given on a display board at the top of the grassy area above Drayton. This was erected in memory of Dr. Andrew Rothstein, a lecturer in geology at Portsmouth University.
Click the small image for a large version (342kB), published with the kind permission of Andrew's family.

Early history

About 10,000 years ago the last ice age ended and with the warming climate, forest spread northwards replacing stunted cold-tolerant tundra vegetation. It is thought that Neolithic man (from 8000 years ago) began clearing the trees from the hill because the soil could be easily cultivated. However the forest clearance also allowed the soil to be eroded, especially on the steep south-facing slope, adding more material to the coombe deposits.
Farming probably involved growing arable crops as well as grazing livestock, and has more or less carried on ever since. Many Neolithic, Bronze Age, Iron Age and Saxon burial sites have been found, along with features such as ancient track ways and enclosures. A description of one such discovery was given in the Hampshire Telegraph, now The News, for Sept. 16th, 1816, summarised here:

While working the chalk pit near the Naval Telegraph a tumulus was broken into and ten human skeletons discovered in good preservation. The tumulus was about 100 feet long, 20 feet wide and 6 feet high. Bodies had been placed with heads to the West. They were assumed to have been killed in battle, as one skull had been penetrated by the iron tip of a pike to a depth of three inches.

The Naval Telegraph referred to was the Shutter Telegraph just west of Candy's Pit.

Sheep Country

From medieval times until the 1940's large flocks of sheep were kept on the hill. Grazing livestock produced a distinctive open grassland rich in specialised plants that can cope with the free-draining, nutrient-poor soil. Agriculture was clearly important as there were several medieval villages on Portsdown. To the north the villages have either disappeared or are represented by a single farm. To the south villages have been incorporated into urban Portsmouth. William Cobbett, 1763-1835, in his famous book Rural Rides comments that some of the earliest and finest corn in the whole of England was grown at the bottom of the hill for many years.
As well as farming there are other reasons why early inhabitants of the area would have preferred to occupy Portsdown Hill. Its slopes form an important defensive barrier and lookout point. It is thought that Roman, Saxon and Norman inhabitants took account of the hill's strategic value.
The hill also provided a safe all-year route through the area even when tracks through the surrounding countryside were impassable due to waterlogging or the fear of attack. It is likely that important routes ran the length of the hill, and from early times these would have encouraged people to settle in the area.
Sight-seeing from the hill is nothing new, and it has inspired at least one poem. Here is the start of a lengthy poem by J.W.Wakely, written in 1840 and dedicated to Sir George Staunton. Italics are used in the original as shown here.

sheep grazing in 1910

Hail fresh'ning eve! now heats intense decay,
To Portsdown Hill I rove - there to portray
The lovely scene expanding wide around,
The woods, the lawns, the rich enamel'd ground;
The distant hills their azure summits rise
From neighbouring vales, and sweep the circling skies;
The silvan beauties of the rural scene;
The vast outspreading of the deep serene;
Whilst thro' the Crab the radiant sun is roll'd,
And whilst the scene is ting'd with ev'ning gold.

For the full work, see "A poem on Portsdown Hill" in Portsmouth Central Library, ref. 821.WAK.

The picture shows sheep grazing in 1910, alongside Southwick Hill Road

From Forts to Follies

Fort Purbrook

The defensive value of the hill was recognised by the Victorians when they built the line of forts along its ridge in the 1860's. Napoleon III had built up a strong navy, provoking exaggerated fears of invasion. If an invader had landed elsewhere along the coast and gained control of the hill, he could bombard ships and buildings in Portsmouth Dockyard, so the forts were built to resist attack from inland. But by the time the forts were finished, the threat from France had disappeared, leading to them being described as Palmerston's Follies, after their main advocate Lord Palmerston.

A front view of Fort Purbrook, now used as the Peter Ashley Activities Centre.

Sadly the construction of the forts destroyed or buried earlier archaeological evidence, while leaving us with some impressive buildings suitable for a wide variety of activities.

The Fall and Rise of Grazing

Highland cattle. Photo : Hilma Miles

Cattle and sheep grazing had died out by 1960, leading to the invasion of the hill not by the French but by coarse grass, scrub and eventually trees. Rabbits would have had a significant effect on keeping the grassland short, but were devastated by Myxomatosis between 1953 and 1955. By the late 1980s it was clear that serious action was required to save the open nature of the hill, leading to the formation of the Portsdown Hill Countryside Project with the appointment of David Cessford as a full-time officer. Scrub control started on a small scale, and grazing was re-introduced. Highland cattle (pictured) are one of many breeds which have done their bit. Horses are used regularly, but the goats were rather too difficult to control in large areas, and attracted too much attention from some local people. Goats are presently being used with great effect to control scrub within the confines of one of the forts. Rabbits have re-established themselves and now have a major effect on the appearance of the hill. The story continues....