When the heatwave hit last month, all Londoners could think about was where to cool off.

And with the city only set to get warmer in the coming years, a new outdoor swimming bible by lifelong enthusiasts John Weller and Lola Culsan offers ideas for rivers, lakes and pools where you can take a dip in and around the capital.

From the iconic pool at Cliveden where Christine Keeler met John Profumo, to Millwall Docks, it features more than 140 of the best including 31 lidos and outdoor pools; 11 hotels and clubs, 46 private lakes, six beaches (Dover, Brighton and Whitstable), and 46 wild swims including numerous places along The Thames.

Of course outdoor swimming isn't just for heatwaves - the Kentish Town residents are passionate year round swimmers who have previously penned books on Wild Swimming Spain and Hidden Beaches in Spain. He's a photographer and travel writer, and she's a former stand up comic who teaches in north west London. Weller's stunning photographs feature expanses of inviting blue water and idyllic stretches of riverbank, alongside practical details on directions, travel, parking, opening hours and prices. There's also information on swimming with a disability, the right to swim, water safety and quality - from the perils of blue green algae to swimmers' itch.

The pair have swum every spot in the book at different times of the year and often travel by public transport or by bicycle. North London spots include the Hampstead Ponds and Parliament Hill Lido, Park Road pool in Crouch End, Hackney West reservoir, and London Fields Lido.

Q: What got you both into outdoor swimming?

John: I was born on Grafton Road near Queen's Crescent. It was definitely trips to Parliament Hill Fields Lido and Finchley Lido that nurtured my love of outdoor swimming. My Dad was a graceful diver; my mum still is an elegant swimmer. My sisters and I spent almost every day during the summer at one lido or another.

Lola: It was summers in Spain with my cousins. I would spend hours jumping over the waves or swimming up them and shooting out of the top like flying fish. It was a big treat to hire a pedalo and go out into deep waters and swim there and compete with my cousins to try and dive deep enough to pick up sand from the bottom.

Q: Were there any new places you discovered while researching the book?

Lola: We loved Guildford Lido - gorgeous and grandiose; possibly worth moving to Guildford for. We found some great places to swim in The Thames, past Hampton Court and beyond. We were also very fond of Wycombe Rye Lido, probably due to the fantastic staff. Newly opened Luxborough Lake near Chigwell was a last minute and magical discovery.

Q: Why do you enjoy swimming outdoors and why has it taken off in recent years?

John: I love swimming under an expanse of open sky, especially when a swan, duck or cormorant joins you or flies overhead. Swimming outdoors makes me happy. There are many reasons why outdoor swimming swimming is more popular than ever: social media; widespread reports of cures for anxiety or mental health conditions; reconnecting with nature. However, I think people swim outdoors because it's all-year-round good fun.

Lola: since going through the menopause, with all the hot flushes and anxiety that brings, I find swimming outdoors in nature really calms me - especially in winter. Cycling to the ladies' pond I feel my thoughts are swarming around me like so many bats. Once I get into the water and focus on the little bits of green growth between the skeletal branches of winter trees or spot a coot nonchalantly gliding across the pond, all the bats seem to melt away and I am truly present in the moment.

Q: There's been concern about water quality recently have you had bad experiences and what advice would you give to swimmers?

Lola: Help campaign for clean rivers. We should have the right to swim safely in any river. The Rivers' Trust involves experts to 'enable rivers to thrive again'. They have an excellent map showing where effluent has been dumped in rivers during the past year. We used this map when deciding which spots to include in our book. Apart from that - keep your mouth firmly shut. We've swum in every spot in this book and have never even had swimmers' itch.

Q What are your tips for swimming safely?

John: Learn to swim properly, it's never too late to learn. Teach your kids to be confident in water. If wild swimming, never swim alone, and keep a constant watch on weak swimmers. Don’t get too cold – warm up with exercise and warm clothes before and after a swim.

Outdoor Swimming London by Lola Culsan and John Weller is published by Wild Things £18.99.