Alert – Helen Fielding beams as she turns up on the set of Bridget Jones for a ‘surprise’ visit to see filming for the fourth and final Renee Zellweger adaptation of her best selling novels

The smile is very much one of a proud mum, or grandmother, enjoying watching her little ones playing in the park. 

How time flies, she’s thinking. How ­grown-up my babies have become.

Anyone passing the throng of people on ­Hampstead Heath, in North London, this week wouldn’t have looked twice at the beaming, middle-aged woman, in wellies and sunglasses, chatting at the edge of the group.

The scene was captured in a series of paparazzi photographs, as the fourth and final ­Bridget Jones film — Mad About The Boy — began shooting.

But eagle-eyed observers soon spotted that the woman, in a cream high-neck jumper, black jeans and very un-starry Ray Ban-style ­sunglasses, was in fact the multi-millionaire author and Bridget’s creator, Helen Fielding.

Anyone passing the throng of people on ­Hampstead Heath, in North London, wouldn’t have looked twice at the beaming, middle-aged woman – but eagle-eyed observers would have spotted Helen Fielding (right) and Renee Zellweger (left) on set of the new Bridget Jones

It was, say sources working on the film, ‘a bit of a surprise’ when she turned up. 

She did, they say, ‘go very much under the radar’, despite her VIP ­status.

 The only clue that she was ‘­someone’ was the lanyard around her neck.

Onlookers say that Helen, now 66, chatted and giggled with Renee Zellweger, who is reprising the role of Bridget, in Hampstead where much of the film is set — and conveniently just down the road from Helen’s own Georgian townhouse.

In the film, Bridget — the erstwhile Chardonnay-swigging, chain-smoking, calorie-counting, 30-something girl about town — is now a middle-aged, ­single mother of two, following the death of her beloved Mark Darcy, and living in the opulent ‘yummy-mummy’ enclave.

A Bridget Jones insider tells me: ‘Helen didn’t stop smiling, she was absolutely loving being there to watch Bridget. 

‘She didn’t make a big deal of herself, she just got herself in a nice position to watch what was going on.

‘It was the first time that Renee had been filming with the ­children, so it was a special moment for Helen. It’s the first time there have been scenes of her being a mum, a really lovely part of the script, so she wanted to be there to witness it. She appeared enormously proud.’

Some might say that it was a case of art ­imitating real life for Helen also found herself in ­Hampstead, living life as a single mum.

Before that, it seemed that like Bridget, Helen had found a late-blooming ‘happy ever after’. 

She had experienced a series of unhappy romances in her 30s, once remarking that she’d had more than one Daniel Cleaver — the bad boy played by Hugh Grant in Bridget Jones — in her life.

While a singleton herself living in Notting Hill, Helen dated ­television producer John Lloyd and war ­photographer Roger Hutchings.

Like Bridget, Yorkshire-born Helen, who attended St Anne’s College, Oxford, where she briefly dated Four Weddings And A Funeral director Richard Curtis, became single again in middle age after separating in 2009 from her long-term partner, Kevin Curran, a TV executive on The Simpsons.

She had ditched London for the bright lights of Los Angeles in 2000 after meeting Curran when she was on an LA-based publicity tour for Bridget Jones. 

The Bridget Jones series evolved from a column Helen Fielding wrote for the Independent. Pictured: Zellweger in the original Bridget Jones’ Diary

 They ­literally bumped into each other in the lobby of her hotel, fell in love, and moved in together.

Curran was a ‘big deal’ in ­Hollywood circles for his work on The Simpsons, winning three Emmy awards for ­Outstanding Animated ­Programme. 

In the 1980s, he picked up three awards for his work on the Late Show.

Later he wrote and produced hit sitcoms Unhappily Ever After and Married … With Children.

In 2001, Renee Zellweger brought Helen Fielding’s Bridget to life on the big screen in a hugely successful movie that earned her an ­Academy Award nomination for Best Actress

As one of Los Angeles’ golden couples, they lived in a gated ­mansion in the ­affluent Hollywood Hills, just around the corner from A-listers such as Keanu Reeves, Halle Berry and Jack Nicholson.

The pair had two children: ­Dashiell, born in February 2004, and Romy, born in July 2006. 

­Curran proposed while Helen was pregnant with their second baby, but they never married.

She said she enjoyed being engaged too much to spoil it.

Speaking of the proposal, Helen said at the time: ‘It was a ­surprise. [Kevin] said he’d got me a present, but I thought it was a slow cooker because I’d been going on about it.’

Helen Fielding experienced a series of unhappy romances in her 30s, once remarking she’d had more than one Daniel Cleaver — the bad boy played by Hugh Grant in Bridget Jones — in her life

Three years later, however, the pair ­quietly went their separate ways, never disclosing the reason for their split. 

She returned to London, and the pair remained close friends. In 2016, the family’s life was turned upside down when Curran tragically died, aged 59, from cancer.

The Bridget Jones series evolved from a column Helen wrote for the Independent newspaper. 

It was hugely successful, leading to the first book in 1996.

Based on Helen’s own life, Bridget worked in the media and lived alone in West London, and charts her hapless attempts at self-improvement in her diary. 

She wanted to eat, smoke and drink less, have ­slimmer thighs — and a perfect boyfriend.

Bridget Jones’s Diary became a global ­phenomenon.

In 2001, Renee Zellweger brought Bridget to life on the big screen in a hugely successful movie that earned her an ­Academy Award nomination for Best Actress.

The second book in the series, Bridget Jones, The Edge Of ­Reason, was published in 1999 and adapted to film in 2004. 

The third instalment, Bridget Jones’s Baby, was released in cinemas in 2016.

Next year’s film will find Bridget in her mid-50s, still her quirky self, but now hooked on social media and dating apps.

Speaking about her character coming of age, Helen said: ‘She is older, so in the same way as I was looking at being a single 30-something in Bridget Jones: The Edge Of Reason, now I’m looking at being older . . . and, yes, looking at motherhood.

‘Where Bridget was trying to be a better girl or sex goddess, to be thinner and eat less, now she’s basically trying not to lose the ­children while checking her ­Twitter followers.

‘Motherhood is certainly a rich seam of comedy. But she does keep the children alive throughout the book, otherwise that would rather spoil it.’

Helen is said to be ‘thrilled’ that Bridget will end life on a high.While nobody working on the new film wants to give away the ­ending, it can be revealed that Bridget is involved with three men. 

After her human rights ­lawyer husband Mark Darcy (Colin Firth in the movies) dies, there is no shortage of male attention.

The fourth and final ­Bridget Jones film — based on Helen Fielding’s last book in the series, Mad About The Boy — has begun shooting

There’s a hunky young gardener named Rockstar, who is played by One Day heartthrob Leo Woodall, Hugh Grant’s Daniel Cleaver makes a welcome appearance, and PE teacher Mr Walker, who is played by 12 Years A Slave actor Chiwetel Ejiofor.

‘The script is utterly joyous,’ says a member of the crew working on the movie. 

‘Bridget has some final flings with this ­scenario and she will be seen having fun, but there will be a sensible ending and one that will warm her fans’ hearts.

‘Helen has given her girl the ­perfect ending, two children and a lovely and pretty normal boyfriend. It is how she wanted it.’

As for Helen, her wedding finger was still bare as she hung out on Hampstead Heath this week with a female friend. 

While it is not known whether she has a man in her life, she can’t stop smiling — and that’s all thanks to Bridget.

‘There was no heartache to be seen on her face, just lots of joy,’ said a source on the film.

And with the movie set for release on February 14 next year, Bridget’s last outing is the best Valentine’s present Helen could have wished for.