Visited the site today to see if I could find the long barrow to the north east, no luck I'm afraid. The undergrowth is very thick at this time of the year and I could easily have walked straight past it.
The barrow on this post is very easy to find, park on the other side of the road in the car park of Martin Down nature reserve. The road here is extremely busy and you can't see very far either way. The barrow is a few hundred yards to the north on the east side of the track.
(SU 03552042) Long Barrow (OE) This is situated near the boundary between Hants and Wilts but is actually in Hants. The mound in 110 ft long and 60 ft wide and is 8 ft high. The flank ditches are 18 ft wide and about 2 ft deep. It is a well preserved example with the mound gently increasing in height towards the SE. The ditch is better preserved on the W.
This barrow measures 38 metres NW-SE and 24m SW-NE. There is a ditch on the W side but only rather vague traces of one on the E side. The barrow is 1.8m in height (slightly higher at the SE end) and 2.4m above the bottom of the ditch.
The fantastic ‘Hampshire Treasures’ resource gives the following info on this scheduled ancient monument, no.430 – “ 135 yds. north of the Roman road, on the Hants/ Wilts border. 38 m. long by 24 m. wide. Ditch visible on west side with only vague traces on the east side O.S.A. No. SU02 SW34.”
The OS map shows another Long barrow in Vernditch Chase about a 1km due North, but I can’t find any information about that one!