Open Garden Squares: peek inside London's secret spaces for one weekend only, from 10 Downing Street to the garden made famous by Notting Hill

One memorable scene in Nineties romcom Notting Hill sees Hugh Grant and Julia Roberts break into the private Rosmead Garden but for one weekend only, Londoners will have the chance to explore it without risking life and limb scaling the iron railings.

Open Garden Squares Weekend returns this Saturday and Sunday to offer people the chance to peek inside more than 230 gardens across 27 boroughs, from the historic and traditional to the modern and experimental.

Some of the gardens are for residential use only, some are not normally open on weekends and others are always open but off the beaten track. Gardens that are usually inaccessible are indicated with a key symbol in the guidebook (full list here).

Now in its 20th year, the popular event serves to highlight the social, cultural, environmental and economic contribution that gardens, squares and green spaces make to London and those that live here.

No other European city has developed the garden square in quite the same way that London has. Today they are a key part of the city's fabric, helping to keep community spirit alive, attracting tourists and offering havens to relax in after a busy day in the office.

Which gardens are opening?

There will be a record 237 gardens unlocking their gates this weekend, with the full list available here.

These include the garden of Number 10 Downing Street where the Prime Minister welcomes high profile guests (available to access through a public ballot only); The Deanery, the Dean of Southwark Cathedral's private residence next to the Globe Theatre; Trumpeters' House nestled between the Thames and Richmond Green with its 18th-century summer house and aviary for doves; the Royal College of Physicians' medicinal garden; Nomura International's huge rooftop garden and The Master's Garden within the Temple complex.

What events are taking place?

Highlights will include a pop-up gin garden serving gin and tonic ice-cream, a botanical art workshop, herbal tea making, exhibitions, plant sales, poetry, live music and talks on bee-keeping and urban farming.

What is there for children to do?

Children can take part in activities such as pond-dipping, seed-planting, storytelling, face-painting and nature hunts, as well as building an insect house and sowing a wild flower meadow.

How much do tickets cost?

Tickets cost £13 if booked before midnight on 15 June and £15 if bought online afterwards or in the gardens. Young people aged 12 to 18 pay £10, family tickets for two adults and up to three young people cost £40 and under-12s go free.

Tickets give access to all gardens (full list here) across the weekend, but you can buy a Sunday-only ticket for £10 from 4pm on Saturday.

You will be emailed an e-ticket to print out and bring with you. Guidebooks are included in the ticket price and available to collect from the City Information Centre in St Paul's Churchyard or a garden. It can also be read online here.

Can I bring my dog?

Gardens that allow dogs on lead are indicated with a dog symbol (full list here).

Can I cycle?

Cyclists can join three different group rides, visiting gardens in the City of London, Southbank and Westminster; Camden and Islington or Westminster, City of London, Bloomsbury and Marylebone.

When do the gardens open?

Check the opening times carefully as they differ between gardens and not every garden is open on both Saturday and Sunday.

Is there a date for next year yet?

The date for next year's event has already been set for 9-10 June.