Dom Joly: Septics just love my Cockney rhyming slang

I'm in New York again and have been filming all week. I haven't done any hidden camera stuff for ages and it takes a little getting used to. When people ask what it's like doing this kind of comedy, I can only equate it with a bank robbery. There's quite a lot of pre-planning involved, but there are also a swathe of unknown factors that you can never fully control. The tension before you are about to film is extreme – once done, however, you get a huge adrenalin rush followed by a subsequent crash. As we are packing a lot of filming into the week, I am totally exhausted from the experience.

I'd forgotten just how draining it all is. It doesn't help that New York at this time of year is like an evil sauna. Anyone sane has long left the city for cooler climes, leaving just the loonies and the workaholics to roam the melting streets. In a bid to avoid the rush-hour traffic, I took the subway yesterday – a big mistake. It must have been 50C and everybody just sat in a soaking heap of sweat praying for their stop to come so they could escape up into the relative relief of the 90 per cent humidity of the streets.

I've seen so many films of New York where kids are setting off fire hydrants and dancing in the spray. I never really appreciated how necessary that actually was to survive the summer. I think they should just turn them all on, a permanent sprinkler system to cool the baking Big Apple.

My crew are a real mixed bunch – Cubans, Peruvians, Cambodians... all the world in a van. Down time between shoots is spent ribbing each other and, as the only English guy, I get a serious amount of flak. It soon becomes clear that Americans still have some seriously misguided views on how we live. For instance, they genuinely believe that everybody in the UK downs tools and sits down for "high tea" every afternoon at four. However much I try to persuade them that this is bollocks, they just won't listen. The truth – that the only reason "high teas" are still served in posh London hotels is to cater for American tourists – falls on deaf ears.

There is also an obsession with the word "bobbies". No matter how many times I tell them that nobody calls our police "bobbies", I am ignored. My assistant director, a gentle giant of a Rastafarian, is obsessed with Guy Ritchie movies. "Whenever I feel down," he opines, "I flip on Lock Stock and Two Smoking Barrels, dude, that movie just puts me in a good mood..." Each to their own, I suppose.

He now plagues me constantly for more Cockney rhyming slang. I am too embarrassed to tell him that I have absolutely zero knowledge of it and so spend the day making up ridiculous phrases for him to use. If, in the future, he ever works on a Guy Ritchie film, I fully expect him to be cast immediately – you'll easily recognise him: a huge Rastafarian with a broad Brooklyn accent firing out Cockney nonsense (or "Bolivian incense" in my version).

Yesterday, we ended up in Greenwich Village and the crew wanted to show me something. There was an authentic London cab parked outside a shop called Tea & Sympathy. I'd read about this place – it was where British expats come to buy their Marmite and Branston Pickle. On one side was a chippy and on the other a little tearoom full of New Yorkers eating delicate little teacakes and sipping tea in fine bone-china teacups. Those in the van looked at me in expectation – presumably I would be wanting to pop in? I thanked them, but explained that I hadn't come to New York for this. We trudged off down the melting streets towards Benny's Burritos, and everyone actually seemed quite relieved. I certainly was.