After one of the fiercest battles of the Cambodian war, Government troops last month re-opened Highway Four, the vital link between the capital, Phnom Penh and the country's only deep-water port, Kompong Som. But since then only one convoy has got through. This week a Visnews cameraman drove nearly 100 miles (140 kms) along the road, the furthest any newsman has been for months. His film shows Highway Four i still virtually closed.