If you are planning a pre-Christmas short break to the Continent this year, you should do so with the thought that things will never be the same again. Apres le Chunnel, le deluge.
Those quiet towns and seaside places in Belgium and northern France that languish in off-season neglect could this time next year be transformed into the formative stages of a bear garden.
In the first working days of the tunnel, its operators, Eurotunnel, expect much of their business to be generated not by people dashing to the Dordogne or Provence but by travellers popping across the Channel for short stays. The volume of this traffic will be determined to some extent by the fares. In the early days, however, it seems likely that these will be at least as cheap as the short-break special fares charged by the ferries. And these are cheap indeed: pounds 75 for a three-day return for a car with two adults and up to three children is one price being quoted.
Whether fares stay low depends on whether ferries remain an effective competitive force - and on how quickly Eurotunnel wants to pay off its borrowings.
Eurotunnel will run its own tour-operating business, which is likely to concentrate at first on short-break packages. Prices for these hotel-inclusive tunnel deals should be especially keen.
We will need to familiarise ourselves with a fresh horizon. The Eurotunnel terminal at Cheriton, near Folkestone, is a little more than 70 miles from central London. For many people the tunnel will put a wide range of attractive French and Belgian cities and resorts within comfortable distance for a weekend break.
The golf courses of Le Touquet will be 116 miles from central London - on a good day three hours' driving time, including the tunnel journey. (On a bad day it could take three hours to get from Charing Cross to the M25.) Offering cheaper room rates and lower green fees, the French resort, with its casino, reasonably priced restaurants and fashionable shops, will be a highly attractive destination - many people may switch their golf weekends away from the West Country or the Midlands.
Resorts such as Le Touquet and nearby, lesser-known Hardelot, 30 miles from Calais, stand in the path of this new Eurotunnel traffic. Not surprisingly, new hotels and golf courses have been built along this coast - the Cote d'Opale - with an energy not seen since the area's pre-First World War tourist heyday.
Already the ferry companies are depositing several hundred cars and passengers in Calais every hour. Eurotunnel will eventually have the capacity to unload similar numbers every 15 minutes. When demand increases, services could operate every six minutes.
The service, to be called 'Le Shuttle', will be operated independently of the inter-city rail services run by the British, French and Belgian railway companies. These will link London's Waterloo with Paris's Gare du Nord in 3 hours and Brussels' Midi in 3 hours 10 minutes (the opening of the high-speed rail link from London to the tunnel will trim 30 minutes off these times).
If Eurotunnel achieves the level of speed and efficiency it plans, the ferries will have to work hard to compete. The projected 60-minute 'motorway to motorway' Le Shuttle tunnel journey from Cheriton to Sangatte, near Calais, compares with at least two hours for a motorway-to-motorway crossing by ferry - this journey from Dover to Calais can often take up to three hours.
Where the Dover-to-Calais run has been something of an obstacle course - show your ticket, get your boarding card, show your passport, show your boarding card - the tunnel journey, they hope, will be quick and straightforward.
There will be no advance booking, although you can pre-pay if you wish. You leave the M20, pay the fare, clear immigration (British and French passport checks will be carried out before boarding), drive on to the next shuttle and head for France - where, once off the train, you drive straight on to the autoroute. Whether things run as smoothly as Eurotunnel hopes remains to be seen. It would be reasonable to suppose that the company will have as many problems in getting the trains and other services to operate efficiently as it has had in getting the contractors to build the tunnel to time and within budget.
One thing is certain: Eurotunnel's plans have galvanised the ferry operators and the Dover Harbour Board into making long- overdue changes to their operating procedures. P & O European Ferries announced this month that from next spring it will operate a cross-Channel service every 45 minutes. Check-in times will also be cut, from 30 minutes to 20.
Dover Harbour Board has met the challenge by drastically streamlining the loading and unloading process. Last month, for the first time, I drove off the ferry at Dover and went straight out of the terminal without stopping - just the briefest pause to wave the passports at the immigration officer.
I believe the ferries will survive. Many people like the sea trip: they enjoy having a meal; they love browsing in the shops and duty-free supermarkets; they appreciate having a chance to relax after a long drive to the port.
But this affection should not be over-rated. It will not take people long to realise that they can take Le Shuttle to Calais and, if they want a break for shopping, they can head for the nearest Mammouth or Auchan hypermarket - or linger over an excellent meal in some jolly country restaurant.
But what of the claustrophobes, those who say that wild horses would not drag them through the blackness of the tunnel?
This anxiety is based largely on a misapprehension about what tunnel travel will actually be like for motorists. During the journey, which will take 35 minutes, car passengers will have to remain in the Shuttle coach with their cars. You do not have to remain inside your car - although there will be nowhere else to sit. There are lavatories in every other carriage, despite the protests of the French, who considered these facilities unnecessary on such a short journey.
At the Eurotunnel exhibition centre at Cheriton, a full-size replica of a car-carrying Shuttle wagon shows these are well-lit and cheerful. On the train, radios can be tuned to a Le Shuttle radio service, which will offer en route information. Electronic signs in the wagons show how far you have to travel to your destination.
Faced with the possibility of a prolonged storm-tossed crossing by ferry or a rapid transit by train through the tunnel, it seems likely even the most confirmed claustrophobe will opt for the latter.
What nobody has yet properly considered is the profound effect the tunnel is likely to have on our lives. When as a child living near Chepstow I watched the Severn Bridge being built, it was impossible to guess its impact on the community. With the opening of the bridge, places such as Bristol and Weston-super-Mare, which had been an interminable ferry journey away, could suddenly be reached in under an hour.
As a result, people who previously had seen Newport and Cardiff as the limit of their social lives were offered a quick route to Bristol and even London.
Those who live in London and the South will no doubt quickly adjust to the fact that, through the tunnel, Bruges is nearer than Blackpool - that Calais can be reached as quickly as Bristol.
The British Tourist Authority says it expects the tunnel to generate an additional 1.5 million tourists to Britain. But given the novelty of the enterprise, it is impossible to gauge how many new people will be attracted to travel - in either direction.
(Photographs and map omitted)