It shows a large group of people gathered around what looks like a circular, stone folly or memorial, and has the name "W. MAYELL MELBOURNE" blind stamped in the lower right corner. The pole in the middle ground may be a flag pole.
The original eBay listing describes it as a "Breedon on the Hill War Memorial Service, circa 1919," and includes a more modern photograph of the memorial. A photograph of the Breedon memorial, situated on the village green, is also included in the Wikipedia areticle on the village. A planning document from the North-West Leicestershire District Council (Breedon on the Hill Conservation Area Appraisal & Study, April 2001) states that the War Memorial was erected in 1926, while a recent meeting of the Breedon parish council (Minutes, 6 Oct 2008) noted that the "memorial needs sign writing renovation."
I suspect that Diane's postcard photo was probably taken on the occasion of the unveiling of the memorial. The clothing worn by the men and women attending the event seems appropriate for the mid-1920s.
Breedon on the Hill Green & War Memorial
© Michael Patterson, courtesy of Geograph and licensed for reuse under this Creative Commons Licence.
This excellent photograph by Michael Patterson, from the very useful web site Geograph, shows the memorial on the village green, with the commemmorative list of names clearly visible.
The reverse of the postcard is unfortunately of a standard design, revealing no further details of either the photographer or the event/location. What is not clear is whether "W. Mayell" actually took the photograph or merely published and/or sold it. Diane's father told her that Mayell had a general store in Melbourne's High Street in the mid-1930s, which he remembered going into as a small boy, but he had no recollection of any photographic business.
Examination of trade directories of the period reveals a little more:
1926-1927 : Mayell's Cafe, restaurant, High Street, Melbourne
1932 : Mayel Walt. refreshment rooms, High Street, Melbourne
1935 : Mayell Walter, confectioner, High Street, Melbourne
While I don't yet have a definitive answer in relation to whether Walter Mayell took the photograph or not, it appears that he probably arrived in the village between the end of the Great War and the mid-1920s, where he opened a shop on the High Street. He may have taken photographs and published them as postcards - he almost certainly sold such postcards in his shop.
Many thanks, Diane, for the opportunity to use this interesting photograph. From what I have read, I have the impression that the mid-1920s saw a great number of memorials to those who fell during the war built around the country. However, I know of no work which gives any kind of summary. It would be an interesting project.
Anon (1926-1927) Midland Counties of England Trades' Directory, republ. on microfiche by Derbyshire Family History Society
Anon (1932) Kelly's Trade Directory, republ. on microfiche by Derbyshire Family History Society
Anon (1935) Whipple's Trade Directory, republ. on microfiche by Derbyshire Family History Society