Thank you to both cc and Linneyl for their info.
I'd kind of figured out what a redoubt was and where Warrenton was as well, but am still a bit confused to see my grandfather in what appears to be a 'regular' soldier's uniform with weaponry.
I'd also surmised that 'Bobs' alluded to Lord Roberts, but as to why the men were so armed in the photo and why the pic was labelled thus- i've no idea!
There's no further info on the back of it, and sadly my grandfather was long gone by the time i arrived on this planet.
However, on a positive note (and probably totally unconnected with the previously posted photos!),i've unearthed a couple more- no info on either pic sadly.
Not even sure my grandfather is in either of them!
Thanks to all for reading this.