By Orla Ryan Business reporter, BBC News

The trick is to have a party that is remembered well into the next year

In a marquee in Chelsea, London, waiters are offering complimentary drinks to office staff.

Lit by chandeliers and the night sky, the marquee is shaded by trees in the grounds of the Royal Hospital, a stone's throw from the Thames.

Kitchen staff are arranging smoked salmon on plates, as over 500 people from ten different companies, step in from the cold.

Few people remember their office Christmas party the next morning, let alone the following year.

But hundreds of events companies around the UK worked to make the party memorable and should now be counting the profits.

Christmas parties are bigger and more elaborate than ever as firms not only spend more but also want more for their money.

Employees, used to fine dining and with ever-rising expectations, are no longer content with a slice of turkey and some old sprouts.

Worth the cash?

Accountants sifting through invoices on a cold morning in January may find it difficult to see the value of parties such as the one held at Chelsea.

Price of a party �15 per head for 1,000 guests - Namco station, with bowling lanes, bumper cars and pool tables �100 per head for 1,000 guests - Old Billingsgate market with a sit down meal, sparking wine, unlimited drinks, disco and live music �250 per head for 650 people - the Natural History Museum with a gourmet five course dinner and a champagne reception, free spirits, big name DJ and goodie bags �1,000 per head for 128 guests - exclusive takeover of Hotel Splendido, Portofino, Italy with a gala dinner and tour of a vineyard, flights to Italy and overnight accommodation Source: www.christmasparties.net

But the intangible feeling of goodwill created by a good party can last well into the New Year, leaving concrete benefits, according to Mike Kershaw, chairman of Ultimate Experience, the party's organiser.

With 17 years in the Christmas party business, Mr Kershaw is a veteran of the business.

"One of the main changes is that people are taking Christmas parties more seriously," says Mr Kershaw, who says spending has more than doubled to �120 per head in the past ten years.

"They are seeing it in terms of employee engagement and motivation, not just a frivolous 'we have got to do that'," he says.

A decent Christmas party can help retain and motivate staff, says www.christmasparties.net's Charlie Hepburn.

Those who offer a slice of plain turkey may be out of favour with staff

Most parties have an underlying theme of gratitude or success to encapsulate what the party is all about, he says.

"If it has been a great year, lets shout about it, or it could be just a case of saying thank you. It has to be given a reason, rather than doing something which is just for Christmas."

Tears of a clown

But for those who find themselves standing alone in a gilded ballroom, crowded with thousands of work colleagues they have never met, the Christmas party is little other than a reminder of the grim realities and anonymity of office life.

Smaller parties can achieve more in terms of team bonding, not least because you are spending time with people you know and may even like.

Parties held at other times of the year can also achieve more and cost less.

The larger venues book out quickly at Christmas and it is often, at least fractionally, cheaper to organise a barbecue in the summer than a three-course sit down dinner in winter, says Mr Hepburn.

Party trouble

As with any party, people have different ideas of what constitutes fun and employers, so party organisers need to be wary.

In his army days, a party wasn't complete "without 15 punch ups", says Mike Huss, now an employment lawyer at Peninsula.

Staff may need to be reminded of the need for appropriate behaviour at a Christmas function

But times have changed, he adds.

Employers that do not celebrate Christmas are labelled scrooges, but those that do are vulnerable to legal action.

"It is almost always a man that has drunk too much and is trying to kiss all the women," says Mr Huss.

A line at the end of the invite or poster warning staff of the need for appropriate behaviour at a company function should suffice, he says.

"While there are millions of parties, and the vast majority go off without problems, there is just the risk that something could go wrong, " says Mr Huss.