A radiocarbon date for the long barrow on the Lambourn Downs, 4 km north of Lambourn, provides it with a venerable status that has not had much influence on its preservation. Corrected in the usual way, the date falls in the calendar range 4200 ± 200 BC. Part of the long barrow not in woodland has been badly ploughed down, and part in woodland has been interpenetrated by tree roots. It was excavated in a peremptory way by Martin Atkins in the 1850s and rediscovered by Leslie Grinsell in 1935. It was so ruthlessly ploughed that a rescue excavation was mounted in 1964 by John Wymer, who found that very little remained of the exposed mound.
Grinsell described it in outline, and following his plan its central axis seems to have been about 74.7° east of north, which is probably true to better than a degree. Wymer’s plan is more detailed, and shows that the ditches were tolerably straight, and had mid-ditch azimuths (corrected for 4.0° compass error) of about 76.2° (south side) and 73.2° (north side). The average corresponds exactly to the figure obtained from Grinsell’s plan. It differs only slightly from that of the Fussell’s Lodge barrow, but so, of course, do the geographical latitudes and horizon profiles at the two places, and the conclusions to be drawn from the two are very different.
Scattered sarsen boulders are still to be found at the eastern end of the barrow, deriving from a chamber there, and at the exposed western end many of the boulders still lying at the edge of the field are what were removed by the farmer, through deep-ploughing. The modern partial excavation of the head of the mound, within the wood, revealed that sarsen boulders in the mortuary area followed a well-defined line (azimuth about 72°). The Lambourn barrow was perhaps a two-stage structure, like those at Wayland’s Smithy and Fussell’s Lodge, containing a primary wooden-framed tomb that was covered over by the present barrow at a later stage.
Atkins, who tells us that a farmer had already dug into it before him, and that ‘human remains and a quantity of black earth’ were found, also unearthed other skeletons. One was lacking its skull—as a result, he thought, of the farmer’s enthusiasm. More recently, Wymer found a crouched burial in a rough sarsen stone cist, together with seashells, but this was not a primary burial. It is unfortunate that the character of the first structure is unknown, and that we are left with only the decrepit remains of the outer barrow as a guide.
The slope of the badly worn mound when Grinsell charted its profile in 1936 was about 2.3° upwards to the east, and an estimate of the barrow’s maximum height to be made shortly suggests that it might originally have been about 3.0°. The critical land horizon (eastwards) is 2.02° and had there been trees on the horizon 10 m tall, the angle would have risen to 2.32°. (Corresponding western altitudes are 1.54° and 1.97°.) It looks very much as though, just as at Fussell’s Lodge, the slope of the barrow was made to mask the distant horizon, as would be explained if the viewing of a rising star to the east was along its spine by a person standing in the natural hollow at its western end. This appears to have been a ditch, judging from old aerial photographs, and Grinsell took it to be such, like those he knew from Dorset barrows, but Wymer did not detect any such ditch.
Accepting an azimuth of 72° for the line of the barrow’s sarsen core, the rising of the star Altair would have been seen at the stated altitude around the year 3960 BC—a very tentative date, of course.
The barrow was certainly tapered, like that at Fussell’s Lodge, and judging by the ditches the taper amounted to only about three degrees. Observation towards the west was also in principle possible, using the natural horizon. Another way of looking at a star on the western horizon would have been to use the gentle incline up to the tomb entrance from the place of the present road (there is no path in that position now). A person of average height would have seen the foreground (land, track) coincide with the far horizon—assuming trees of more or less 10 m. The high end of the tomb, at 2.6 m above the surrounding ground or thereabouts, would have made a third (intermediate) horizon for the ray to skim, rather as at Wayland’s Smithy, which is less than 5 km away. The artificial altitude would in this case have been 2.0°, which is the extinction angle for the most likely star in that direction, the setting star Aldebaran. There is little point in setting down what are no more than directed guesses, based on a very superficial survey, but a line of sight of azimuth 250.5° would have been needed for the fortieth century BC, not far from the reverse of the supposed direction to Altair’s rising. Both of these alignments might have been embodied in a set of scaling posts, as at the head of the barrows at Fussell’s Lodge and Wayland’s Smithy.
Another possible observation along the barrow to the west could have been in connection with the setting of the Pleiades at the same period, as at Wayland’s Smithy. Not enough detail is known of the Lambourn structure to speculate on a precise alignment. Another long barrow over which the setting of the Pleiades might have been observed is at Nutbane, in north Hampshire, 20 km or so from Stonehenge, a barrow that is perhaps five centuries younger.
The use of the Lambourn barrow as an artificial horizon for crosswise viewing admits of two distinct solutions. One of these involves the setting Arcturus to the north together with the rising Bellatrix to the south. The estimated date (4272 BC) fits well with the corrected radiocarbon date of 4200 ± 200 BC, and yet reluctantly the solution must be rejected. It requires viewing in both directions at an angle of approximately 19.0° to the horizontal, a figure that implies a mound 4.7 m high, seemingly much more massive than the ditches could have provided.
The alternative solution, which is tentatively accepted, is that the setting of Vega was observed to the north and the rising of Sirius to the south, around the year 3970 BC, both stars being viewed at an altitude of 11.0°.11 The implied maximum barrow height (2.6 m) fits very well with what is known of the ditch sizes and their potential for providing material for the mound. The derived date is probably not in error by more than a century. The dates obtained for Altair and Aldebaran along the barrow’s length are compatible with it, but why then does it not square with the radiocarbon date?
The latter was based on a patch of burnt wood from the floor of the tail end of the south ditch. It could have originated with timber from an old mortuary house, or from posts that had been removed from an old structure by burning—broadly speaking, the bigger the post the older the timber. As one of the long barrows at Skendleby will later demonstrate, a set of more than a dozen radiocarbon dates from a single site may span two millennia, and any one of them in isolation might have given an entirely false impression. In a sentence: the Lambourn barrow we (barely) know is perhaps not as old as is generally supposed.
Although the Lambourn barrow is now in a relatively isolated spot, there was considerable later prehistoric activity nearby. It is unlikely to have been by chance that, almost in line with it, and half a kilometre to the east, is a disc barrow. Mostly to the southeast of it, and within a circle of radius under a kilometre, there are remains of at least thirty round barrows of various types of the early and middle Bronze Age. A dozen of these lie together in a group with the collective name of ‘Seven Barrows’ (the English having always found barrows difficult to count), and six of them lie virtually in a line that passes directly over the long barrow, while another four lie roughly on another line, parallel to the first. The former and better alignment is about 40° north of west (or south of east), but this depends on how one selects the barrows, for the line is not perfect. It seems obvious that these much later tombs were aligned on the setting of the Sun over the long barrow at the summer solstice—a direction which changed very slightly with historical period. (The calculation depends on the horizon altitude, which in turn depends on the line chosen.)
It is hard for us now to comprehend how such a simple mound as the Lambourn long barrow could have kept its reputation as a place of great sanctity for perhaps two thousand years after it was first erected. Having accepted the idea, however, we seem to catch a glimpse of one reason for shifting allegiance away from the stars to the Sun in these matters of alignments: the directions of the Sun’s risings and settings are more or less constant over very long periods of time. For most of the stars this is not true, even though Deneb, as we have already seen, had a certain constancy in its behaviour.
One of the most valuable of