[garm]

Looking at the link which the OP gives to the National Gallery, I see they've dated the colour picture of Tolkien as September 1961. I think that's a mistake on their part. Chandler visited the Tolkiens twice: in 1961 and again in 1966, when she took photos of Ronald and Edith on the occassion of their 50th wedding anniversary.

One of the 1961 pictures - that is, the black and white one shown on the National gallery website - was used as a frontispiece to the 1962 festschrift _English and Medieval Studies Presented to JRR Tolkien on the Occasion of his Seventieth Birthday_, ed. by Norman Davis and C.L. Wrenn. This book is further distinguished in that it has a facsimile signature of Tolkien's, under the photograph, leading some to believe that it's a 'real, signed copy'.

There's a set of these photographs available; five colour, all of 1966, and three from 1961; these are black & white. They all have the year of copyright printed on the reverse. They make a very nice set.

There was a display of prints of these photos at last year's Oxonmoot (the annual weekend conference of the Tolkien Society). It was possible to order high quality prints, in various sizes. The largest of these was very large indeed; the type you'd most likely see framed on the wall of a museum or such like. I didn't order any; I'm quite happy with my set of post card sized pictures.