And if you get stuck, there is always an expert with their own RV to help. Forget trailer trash, this is middle class America on holiday and politeness and courtesy levels were switched to smiling maximum even when my 10-year-old daughter, on being told by a family that they were from Pennsylvania, replied: “What, like Dracula?”

HOW WE PLANNED THE HOLIDAY:

Booking flights, hotels, RV pick up, campsites and planning a route sounds a nightmare but all I can say is thank God for Google.

Flights were the biggest expense, naturally, but having been quoted up to £800 a head for direct flights with BA we went to Expedia and looked up options to go indirectly. It came up with North West airlines, changing at Minneapolis for around £600 a head for the five of us.

Hiring the RV was a completely new experience. We Googled RV hire and two companies kept coming up – El Monte and CruiseAmerica. After comparing prices offered by agencies, the best we could find was from a UK-based company SDSA Promotions who were incredibly helpful.

If you fly to the US, the law insists that you spend a night in the country before hiring an RV so we booked a hotel next to the Mile High Stadium, home of the Denver Broncos US football team, the night before, which we also found on Expedia.

We had already planned out route by buying a map of Colorado and Wyoming from Stanfords bookshop in London and if buying online, it is easy to get one map covering both states. We also bought a guide book on Yellowstone and the Tetons – and there are loads available. Just make sure you get one with local maps and routes of the National Park.

But there are suggested routes from Denver of the official Yellowstone Park website, and if you go to the park service website there is a great webcam of Old Faithful, updated every few seconds.

We had ten nights of campsites to fill and booked the first six nights in advance but for the last four, played it by ear and looked for places while on the road. Despite being peak season in America, we found vacancies pretty easily.

For the first couple of nights we stayed near Denver in the picturesque Estes Park which we found on www.nationalparkretreats.com but, surprisingly, had to ring them to make the booking as they didn’t do it online. But it was a very well run site with loads of facilities.

On the way to Yellowstone we spent a night at the odd Fountain of Youth RV park in Thermopolis run by the equally odd but friendly Ron Foote. It boasts a huge swimming pool naturally heated by the town’s famous thermal springs. It’s like swimming in a bath but one which needs a lick of paint round the edges. Ron’s laid back and you don’t have to pay till you get there.

The officially run parks in Yellowstone are operated by Xanterra Lodgings on www.travelyellowstone.com and to stay at these sights does require advance booking usually so we sorted out a couple of nights at Fishing Bridge in the middle of the park and slap bang in grizzly bear country.

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