The headteacher of an exclusive all-girls school has not returned after the Easter holiday having announced her resignation earlier this year.

Jenny Stephen was due to remain at South Hampstead High School, in Maresfield Gardens, Hampstead, until the end of the academic year but has left a term earlier than planned in a move which has heightened the mystery surrounding her departure.

A statement released in January by South Hampstead High, a top independent school which boasts Hollywood actress Helena Bonham Carter and author Fay Weldon as former pupils, said Mrs Stephen would be leaving at the end of the year for “professional reasons”.

But a spokeswoman for the Girls’ Day School Trust (GDST), which South Hampstead High School is part of, said it had since “been agreed” that Mrs Stephen would be “stepping down early, at the end of the spring term”.

GDST recently appointed Helen Pike as Mrs Stephen’s replacement.

Ms Pike, currently director of studies at Royal Grammar School, Guildford, will take up her new role as headteacher at South Hampstead High in September.

In the interim, the school will be led by Libby Nicholas, currently the GDST’s deputy director of education and previously deputy headteacher of the GDST’s Sutton High School.

The school, for four to 18-year-olds, split between a junior and senior site, charges parents up to £4,560 per term.

In recent years, Mrs Stephen had overseen a redevelopment project at the school, which has so far seen the demolition of a Victorian building on the senior school site which is set to be replaced with a modernist glass building due to open next year.