As many as 40,000 holidaymakers have been hit by the collapse of a travel company, with many Christmas and New Year trips cancelled.
About 10,000 people were due to travel over the festive period, and 30,000 next year, with Gloucester-based Travelscope Holidays.
All will have the full cost of their holidays refunded, administrators said.
More than 200 people are likely to lose their jobs and the firm's boss said he "deeply regretted" what had happened.
Managing director Richard Ford said he had held off putting the business into administration until he had paid all the staff their December wages.
He said: "I deeply regret the disruption caused to so many people.
"We've been trading 15 years now, we've had a very good reputation and been profitable every year and I deeply regret this happening, particularly at Christmas time and also for our own staff.
"The total responsibility for this is mine - I'm the managing director and the only shareholder of the company."
Some 854 passengers due to travel on Saturday were told they could not do so.
Joint administrator Paul Clark, of Menzies Corporate Restructuring, said: "At least one call was made to every single one of those passengers on the numbers we had on the company's documentation.
OTHER TRAVELSCOPE TRADING NAMES REGISTERED WITH ABTA
TSI Business to Business)
Travelscope for Groups
Travelscope Air Holidays
Study the World
River Cruise Collection
Ocean Cruise Collection
"We reckon about 80% we contacted. Valiant attempts are being made to contact all these people.
"We've now got another 1,900 people that need to be contacted for trips for the next few days.
"This is a very, very busy time for the Travelscope business."
People whose holidays have to be cancelled will receive refunds, with the Civil Aviation Authority (CAA) covering payments for air passengers, and land and sea passengers receiving refunds from the Association of British Travel Agents (Abta).
Mr Clark said he believed everybody on holiday at the moment had been contacted and that the CAA and Abta would cover the cost of completing those holidays.
More than 460 passengers who are currently on the cruise ship MV Van Gogh, which is due to return to the UK at Falmouth on 4 January, will be free to finish their holiday interrupted.
'Lonely at home'
Customer June Dolphin, from Stroud, said she had been due to head out to Austria on Friday night, having paid £743 in cash for her trip.
She said: "I've had no information at all and I am gutted.
"We were going to have a sleigh ride on Christmas Day and a steam train ride on Boxing Day. We don't like Christmas at home, it's too lonely."
Abta said people who had booked Travelscope holidays through a travel agent were being offered alternative trips.
Spokeswoman Frances Tuke said: "Where possible those who have booked through a third party are being put on different trips.
"For example, I know that the Co-Op has rearranged for many of its customers to go on coach holidays today. They have acted very quickly."
Travelscope employs 270 staff, who are mainly based at the Gloucester offices.
Mr Clark said: "The staff have been absolutely fabulous. Certain of them who were not due to be working have actually come in to try to help the situation.
"You need to look at that against the backdrop that just yesterday I had to stand up in front of 250 or so people, making it clear to them that I expected the vast majority, possibly all of them, will lose their jobs."
He said administrators had received several expressions of interest but, given the time of year, discussions had developed slowly.
Travelscope blamed a cancelled cruise for the firm's financial problems.
"I'm very, very sorry," Mr Ford said.
"I had tried hard to speak to the administrators before about continuing the company into the New Year but we were advised this wasn't an option."
'Very sensitive time'
Mr Clark said: "The company would have run out of cash over the next few days."
He said if the administration order had not been made when it was, some people whose forthcoming holidays had been cancelled would instead have gone on their trips only to be left stranded abroad.
He said: "The fear, of course, particularly over this very sensitive time, is whether hotel owners or coach owners or other people who are carrying them around said 'if I am not going to be paid, you get off my coach, you get off my boat'."
Travelscope Holidays Limited was established 15 years ago and provides worldwide escorted tours.
In its last accounts filed with Companies House, the firm reported a turnover of more than £75m in 2006, with a pre-tax loss of almost £2m. It owed some £20m.
A company spokesman said the most recent annual turnover for the business was £80m.
Abta said it represented more than 1,500 travel businesses, of which 25 to 30 tended to go out of business each year.
The Abta phone number is 01243 621500