'Look, there is no right or wrong. If you think it is right to have sex on the first date, then it is right. Two consenting adults can do what they want to do.
'People will say all sorts of things, like if you give in too easy it is not going to be good at the end. I think that is all rubbish. I say, if it feels good, do it!' bellows Fred.
We meet at Galvin at Windows, the Michelin-starred gastrodome on the 28th floor of the Park Lane Hilton in London, where Sirieix has been the general manager since 2006. This is his real job in his real restaurant, and this lunchtime it is full of happy diners feasting on Isle of Wight heritage tomatoes, beef fillet and caramelised apple tarts. There is the pop of a champagne cork, the hum of conversation.
Fred sits at a quiet table near the bar, dapper in his blue Cerruti suit and pink shirt, his enamelled French Tricolour cufflinks gleaming as he sips a mint tea and cuts to the chase. 'A woman's body is a beautiful thing. Why try to hide it?' he says when I ask if first-date dressing should mean that modesty is the order of the day.
His pale blue eyes blaze and his accent is as ripe as a Roquefort cheese, one with a pungent vein of madcap energy running all the way through.
Now 44, Sirieix has spent his professional life in the restaurant business. He had no plans to be on television and was reluctant to take the C4 job when it was offered - 'I didn't want to do it!' - but eventually did so because he realised it might be fun. Now he gets stopped on the street and has become a star himself.
'People call me a celebrity. I am not a celebrity!' he says, still astonished by his fan mail and constant demands by star-struck followers to take a selfie with him.
'I am happy to do so, but please, ask first,' says the man for whom manners mean so much.
Don't you just love First Dates? No, not the anxious, stumbling, reality of a proper first date with an actual human being, but the Bafta-winning Channel 4 reality show which plays Cupid with complete strangers and has become a big hit, with more than two million viewers.
Since its launch in 2013, the show has filled the heart-shaped hole left in British television schedules by the abrupt end of Cilla Black's Blind Date in 2003.
So far, more than 100,000 hopefuls have applied to be on First Dates and following the current celebrity version, the next series will start in the autumn and run until 2017.
The format is simple. Lonely hearts couples are paired together in a London restaurant (it is actually Paternoster Chop House near St Paul's Cathedral, which is closed to the public during filming) and then filmed over the course of an evening as they enjoy drinks and dinner.
Hidden cameras capture every excruciating moment, from the spark of possible mutual attraction over the potted shrimp starter to potential tears over the tiramisu dessert. At the end, the prospective couple are quizzed about the chance of them going on future dates.
There have been some unforgettable moments. A fortysomething woman called Jo cried when Gus said no to a second date in 2014. Meanwhile, gay couple Adam and Dan are still together.
But Scott and Victoria, who met eight months ago and got engaged at Christmas, have just split up. A shame, because Fred was planning to go to their wedding. 'Oh no, they were so lovely together,' he says. There are Irish and Australian versions of the show, but none of them are as successful as the UK original, and much of this is down to Sirieix himself.
He presides over the First Dates restaurant with the natural authority of one who worked his way up the hospitality trade the hard way.
He came to London 24 years ago, and started in the kitchen at La Tante Claire - and it's his irrepressible joie de vivre that gives the show much of its warmth and charm. 'What a smile you have!' he said to one female contestant - surely the best chat-up line ever.
Between the dates of varying success, the camera turns to Fred, who shares his musings on the developing romance, on love and on life in general.
These bon mots are inspired by his favourite philosophers: Socrates, Marcus Aurelius, footballer Thierry Henry, Shakespeare and Fred's own dad, a hospital nurse from Limoges. 'What has matured the cherry will mature you,' Monsieur Sirieix used to tell his energetic son.
In his new book First Dates: The Art Of Love, published by Viking in September, Fred shares his recipe for a perfect match and quotes one of his favourite sayings by Mother Teresa: 'Some people come into your life as blessings and some come into your life as lessons.'
'But what is most important, the blessing or the lesson, hmmm?' he muses. 'Everybody needs someone to cuddle and give them a bit of love. Being single is not a disease. What is important is being confident and happy within your skin.'
Sirieix is giving me his total attention, while somehow still keeping an eye on the room. What a pro! Every now and then, his eyes glide over to the reception desk, to check that guests are being met and greeted properly ('you must smile before they do') and everything hums with slick efficiency.
Sirieix is the creator of a hospitality training programme called The Art of Service, and his charity work includes supporting underprivileged youths and operating a charity called The Right Course to help young offenders run restaurants inside prisons and get jobs on release.
He is also a runner and an amateur boxer, someone who cycles six miles to work every morning and can't put on weight, no matter how much he tries. 'And I try! I work in a restaurant, after all.'
For breakfast today he had a two- egg omelette and an avocado, for lunch he had gnocchi, halibut, a salad with some asparagus and some puréed peppers. He will have an ice cream at 3pm, a soufflé or a tart before he goes home and then dinner around 7pm.
Fred has two children, Andrea, 12, and Matteo-Lucien, seven, by his partner of 12 years. They never married and are no longer in a relationship, but they live together in the same house in South London. 'It's complicated,' he says. He is now in a new relationship and is happy. 'And that is all you need to know.'
On the show, he was asked how many times he had been in love, which he concluded had been about five times. 'I have had my heart broken many times and I am sure I have broken hearts, too. But if it happens, c'est la vie.
'You have got to take it and move on. People can think of me whatever they want but I am just a normal bloke. I am not the maître d' of love or the love guru.'
Oh, but Fred, you are! You really are. Even here at Windows, he works his love magic all the time. For a start, he always helps nervous diners who want to propose to their girlfriends over dinner.
'I will say, "OK, give me the ring, I will take care of everything." And we will present it under a cloche after dessert.
'But the other day, this guy was so nervous I said: "Right, we are doing this straight away. Put the ring under her napkin RIGHT NOW. I will bring you some champagne. Ask her when she sits down."
'You have to know what is right for them, even if they don't.'
Surely only a love guru would know? Fred fixes me with his blue stare. He believes that to understand love you have to understand yourself. He believes that you have to look deep inside yourself to access it. He believes that some people have been traumatised by love ('You see them on the show'), but that love will triumph in the end.
'When it is right, you can almost cut it with a knife. It is so thick, you can see it,' he says. 'When it is wrong, pfff! It just melts into nothing,' he says, with a Gallic shrug.
And girls, if all else fails, he has one solution. 'I will always love a woman who smells nice. My nose is king!' he cries. 'Cristalle from Chanel is an all-time favourite.'
