It is situated just east of Parliament Hill and north of Gospel Oak railway station.

In the mid-19th century, Ellis founded a number of schools (named 'Birkbeck Schools' after George Birkbeck, adult education pioneer and founder of Birkbeck University, London) and inspired many teachers to promote his educational ideas.

Ellis wanted children to be taught "useful" subjects such as science (including "Social Science"), and to develop the faculty of reason; this was in contrast to the learning by rote of religious tracts, ancient languages and history, characteristic of many schools at the time.

Pupils at least between 1951 and 1955 walked to Belsize Park Underground and thence to Edgware by train holding cardboard tickets, later would be ferried to and from the fields by coach on their appointed games afternoon.

Much ingenuity had gone into extending and converting the building to provide the additional classrooms and specialist accommodation required by the post-war grammar school's large sixth form.

In March 1977, a group of parents tried to get a High Court injunction to stop the governors changing its grammar school status, organised by Dudley Stanley Fox.

With the provision of better facilities for the national curriculum and for information technology the School became fully comprehensive in the years after 1978.

Languages on offer include French, German, Spanish, Mandarin Chinese, Russian and Bengali.

Rose (who had begun his career at the school in the 1970s, and was now Director of the Sixth Form consortium) was appointed Acting Headmaster.

[9] In the summer of 2019, 84% of William Ellis students entered the English Baccalaureate compared to the national average of 29.70%.