For much of its history, it operated as a private girls' school for ages three to eighteen, with boys included at nursery, and occupied three modernised Victorian houses on Castlebar Road.

[3] It was named after Heidelberg, Germany, the birthplace of Chrystabel Watson’s mentor,[3][4] and was originally located at 67 Gordon Road in Ealing.

[3] They opened a private girls' boarding and day school,[6] and in 1898, they moved into a larger house on Castlebar Road.

[7] In July 1915, it was renamed Harvington College, after parents voted in favour of "a British and not a foreign name".

[4] At the start of the Second World War, the school evacuated once again to Barton-on-Sea,[12] and sold two of its four buildings to Middlesex County Council.

[14] The Watson sisters were replaced by two new principals, Mrs. H. K. M. Turner and Miss E. E. Emerton, who had both worked at the school for many years.

[2] As of 2015, Harvington Prep was in three adjoining Victorian houses, equipped with a sports hall, science laboratory, and facilities for music, art, and drama.

[12] Old Harvingtonians have included a former international lacrosse player for England, and a Foreign Office employee who was awarded an OBE.