African anthus armchair tick?

With the flock of 3 Richard's Pipits at Aberlady I managed some good looks at this species for the first time (although, predictably enough, my shots are nowhere near as good as some of those on Birding Lothian). As I mused that I have managed to catch up with very few large pipits over the years I remembered this unidentifed Anthus that I photographed in Hluhluwe, South Africa in April 2007.

On that trip I had been overwhelmed by amazing mammals and jaw-dropping birdlife - larks and pipits had been firmly relegated to their little brown job status and this photograph has remained unidentified ever since. It would definitely be a tick for me, but the challenge is can the species be determined from this single image? The contenders, in descending order of likelihood could be African Pipit, Long-billed Pipit, Buffy Pipit and Plain-backed Pipit. Any ideas?

Whether it is identifiable or not, its presence was eclipsed by a pair of Martial Eagles mating nearby and a close fly-past by a squadron of White-backed and White-headed Vultures. No offence to the pipit, but watching amazing raptors to a backdrop of white rhino is birding KwaZulu Natal style!