It was Somerset Maugham who said the French Riviera is “a sunny place for shady people” – and looking around at all the 'models' in the hotel lobbies and the men in dark sunglasses who seemed to know them, I knew what he meant. Behind the festival's shiny facade, there is an unseemly side – and beneath the azure waters, a polluted mess. The French diver and environmentalist Laurent Lombard's video of the Cannes seabed strewn with waste and debris went viral before the festival began. We were assured there was no danger to swimmers, and the mayor had it cleaned up according to the Daily Mail – but the Med had certainly lost some of its sparkle.

As the stars' private jets swooped in, the internet was going mad for 'the Dad bod'; the slightly flabby male physique was trending and there were plenty of examples on screen. Deborah Cole of AFP noted a “sweating, panting and shirtless” Gerard Depardieu in Valley of Love and a flash of Joaquin Phoenix's “tubby tummy” in Woody Allen's Irrational Man. When Colin Farrell strode the red carpet for the premiere of The Lobster, he looked his usual trim self – but in the film he is distinctly paunchy. To add some girth for the role of a lonely singleton in Yorgos Lanthimos' absurdist black comedy, Farrell went on a massively calorific diet that included drinking melted ice cream, he told the Hollywood Reporter. Eating “two cheeseburgers, fries and Coca-Colas, and two slices of chocolate cake at 10am is not that fun,” he said. “And I love cheese¬burgers."

“Selling out!” “Pandering to the Americans!” The cries went up immediately when the official selection was announced. The list of directors crossing over to make films in English was a long one including the Italians Matteo Garrone and Paolo Sorrentino, Yorgos Lanthimos of Greece, Norway's Joachim Trier and even Guillaume Nicloux of France, a country whose cultural establishment is highly sensitive to the creeping Anglophone menace. The argument goes that Cannes is supposed to be a haven for world cinema; for English, there is Hollywood. But does it really matter? Films at Cannes in languages other than French or English play with subtitles in both languages – and that's a lot of text to deal with.

Cannes' heckles and jeers are famous and the first film to fall foul of this tough crowd was Gus Van Sant's Sea of Trees, which was greeted by a storm of raspberries and thunderous boos at its press screening. Because these take place before a film receives its black-tie premiere, word quickly gets around and can cast a pall over the big event. When Naomi Watts and Matthew McConaughey took their turn on the red carpet, it had “a horrifically compelling walk-of-shame quality” according to the Daily Telegraph. But the Texan actor put on a brave face at a press conference shortly afterwards. “Anyone has as much right to boo as they do to ovate,” he said. I think we know what he meant.

It's a bit of a lark organised by UK film critics – a gong for the top canine performance at the festival, handed out on the last Friday in the British pavilion. This year the Palm Dog went to Lucky, a Maltipoo – that's half Maltese terrier, half poodle – who plays Dixie in Miguel Gomes' six-hour epic, Arabian Nights. The prizewinner is presented with a toy bone and this year delivered a brief acceptance speech (“woof”) by video link. A jolly time was had by all but an unnamed French journalist felt that the award was “an unwanted intrusion of British silliness” in the glamorous proceedings, according to AFP. “From the French perspective, this is a bit bizarre,” he is reported to have said. “The British are weird.”

It was all work, work, work for the BBC Culture team and parties, alas, were few and far between. But the rest of Cannes was painting the town red. In 2013 we tried to calculate the amount of champagne consumed at the festival by contacting Piper Heidsieck, “the official drink” of the festival, but they declined to comment – though judging by the merry faces and staggering gaits of some on the Croisette, it's safe to assume a colossal quantity. At the party for Matteo Garrone's Tale of Tales on the first weekend, the champers flowed freely and the revellers stayed on until the early hours. When the BBC's Rebecca Laurence spoke to one of its stars the following morning and asked how many hours sleep he'd had before their interview, he simply narrowed his bleary eyes and held up two fingers.

It was billed as the year in which female film-makers and women's issues would be in the spotlight. The festival opened with a film by a female director for the first time in 28 years, Isabella Rossellini chaired the Un Certain Regard jury and Salma Hayek convened a high-profile panel to discuss the role of women in cinema. There was plenty to talk about – but had anything really changed? The numbers seemed to speak for themselves: of the 19 films in competition, only two were directed by women. And then came 'Heelgate' – of which, more later… Faced with suggestions that the festival is sexist, artistic director Thierry Frémaux was having none of it. Cannes was being held to an unfairly high standard, he claimed, one not applied to other festivals like Venice or Berlin. His suggestion? Instead, people should “attack the Oscars”.

The biggest story of the festival had nothing to do with films. It was about shoes. On Tuesday trade magazine Screen reported that a group of women had been denied access to a screening of Todd Haynes' Carol because their footwear – flat shoes with rhinestones – was unsuitable for the red carpet. Further tales came tumbling forth, social media erupted in indignation and soon enough we were soon dealing with a fully fledgedscandale. The Cannes press office rushed out a garbled statement: “Rules have not changed throughout the years (Tuxedo, formal dress for Gala screenings) and there is no specific mention about the height of the women's heels as well as for men's. Thus, in order to make sure that this rule is respected, the festival's hosts and hostesses were reminded of it.” Well, that cleared that up. Perhaps wisely, press screenings are exempt from any dress code: scruffy journalists are free to ascend the Palais' steps in flip flops and trainers.

It was the lesson of the UK general election and it's the big 'takeaway' from Cannes too: prediction is a mug's game. All week the chatter was that Todd Haynes' lesbian love story Carol was set to collect the Palme d'Or – or that Holocaust drama Son of Saul from first-time director László Nemes would triumph. In the last few days a consensus began to form around The Assassin from Taiwanese director Hou Hsiao-Hsien; according to British bookmakers, The Lobster was the one to beat. But when Jacques Audiard's Dheepan was announced as the winner, the response was a collective “really?” For all the pundits, critics' panels, insider gossip, statistics and God knows what else, few had picked it. Oh well: c'est la vie.