Winston Churchill's alma mater Harrow is announcing a 'partnership' with an all-girls boarding school for the first time in its 450-year history.

Harrow, North London, is one of the last-remaining full boarding schools for boys but  is now joining forces with the all-girls Downe House School in Berkshire in a new 'structural' alliance.

The schools will retain their own leadership teams, sites, identities and traditions but will benefit from a 'programme of joint academic, co-curricular, and social activities'.

Harrow, which charges £63,000 a year, was founded in 1572 under a royal charter from Queen Elizabeth I.

It has educated seven British Prime Ministers in total, with other notable alumni including the poet Lord Byron and actor Benedict Cumberbatch.

Its decision to partner with Downe House, a day and boarding school founded in 1907 and costing up to £60,000 a year, comes amid growing financial pressures on the sector.

Last year, Labour imposed VAT on school fees and also removed business rates charitable relief for private schools.

However, while the partnership is likely to offer some opportunity for pooling resources, it is understood the main motivation is greater collaboration and sharing of expertise.

A Harrow source said: 'The motivation for this partnership is not financial. Harrow School and Downe House are both thriving. They are financially secure and enjoying strong forward momentum.’

Emma McKendrick, headmistress of Downe School, said: 'Harrow and Downe will both remain single sex. In fact, maintaining our single-sex status and our strong boarding ethos is key to both schools. However, we will be developing a programme of collaborative academic and social activities for our pupils, sharing of expertise for our staff and joint events for our alumnae.'

Alastair Land, head master at Harrow, said: 'Today is an exciting and progressive launch of a new partnership, rooted in traditions, that enshrines the values of unparalleled holistic education in the single-sex boarding setting.

'Harrow and Downe House will be working together to enhance the best of what we do for our boys, our girls, our parents and our staff.'

The two schools said the move was 'a natural and strategic next step' in an already well-established relationship.

Staff will be able to share 'technology and assets' and from 2028, the schools' two calendars will be aligned.

However, they will remain within their separate charities, under their existing boards.

Boys' schools have come under pressure in recent years to provide more opportunities for their pupils to socialise with girls, to combat the rise of misogynistic influencers online.

Major boys' schools to announce co-ed plans recently include Magdalen College School in Oxford and Tonbridge School in Kent. 

David Eyton, chair of foundation governors at the John Lyon's Foundation, which governs Harrow School, said: 'In a changing environment for independent schools, we are excited by the opportunities of working more closely with Downe House.'

Sally McNair Scott, chair to the Downe House board of governors, said: 'By combining our complementary strengths, we will create meaningful opportunities for both girls and boys.' 

Churchill attended Harrow in the 1880s, where he had a poor academic record and only made it into Sandhurst for his military training on his third attempt.

However, when he visited the school as Prime Minister in 1940 during World War II, pupils sang a song in his honour.

Among the alumni of Downe House is the Princess of Wales, but she left after just two terms due to bullying.