When Siobhan Moore, 29, started her first job teaching French, she quickly became friends with a colleague. "I'd felt isolated during the first few weeks," she says. "It was a new town, new job and I was nervous. I was grateful when Tricia picked me as her friend." The two women often lunched together and started going out after work.
One night, after a few drinks, Siobhan told Tricia how attractive she found their head of department, and that she felt he liked her too. "As soon as the words were out of my mouth I wished I hadn't said them," Siobhan recalls. "Tricia began pumping me for details. Had he flirted with me? Had he touched me? She wanted to know every nuance, when really there was nothing to tell." Siobhan went home and spent the whole night worrying about whether Tricia would keep it to herself.
Friendships at work are a tricky business and it's difficult to know where to draw the line. Reports last week that Peter Mandelson failed to invite the fuming Geoffrey Robinson to his housewarming party - when Robinson as a "friend" had himself bankrolled the property - underlines how tender work friendships can be. Now an angry Robinson is planning a tell-all book about his time in government.
Siobhan, like Robinson, was lulled into a feeling of trust and security, and left feeling exposed. "The next day the innuendo began," says Siobhan. "Trisha winked at me whenever we were in the staffroom together, caught my eye if he was around. I was sick with embarrassment." Fortunately for Siobhan the situation did not develop. She managed to deflect Tricia's interest, her "romance" came to nothing and the friendship survived - just. "I learnt a lesson. Tricia and I still had lunch, but I joined a gym and found my social life separately. It was a relief."
The trick, according to Dr Jan Yager, sociologist and author of Friendshifts: the Power of Friendship and How it Shapes our Lives is not to confide in the first place. "Don't tell a work friend anything that could have an impact on your job or give your colleague power over you," she says. "Sabotage of a promotion may be unintentional, but it'll hurt."
Yager advises, while not actually lying, "withholding" information. "You need to determine what it is appropriate to share at work. And work is the crucial word here; that is where you are. Camaraderie is an extra to your job."
According to Dr Yager, spilling secrets to work colleagues is a particularly female trait. "Men learn at an early age never to say or do anything that will derail their rise to the top, and women need to think the same way if they want to climb the ladder," she says. Because women come from a background of openness, or what Dr Yager calls "coffee clutching", they should curtail the amount they share by developing a gut instinct for what may or may not be risky for others to know. "Just be savvy," Yager says. "Steer away from personal information or strong opinions as much as possible."
The trouble is, as Judy James author of The Office Jungle puts it, "Making work friends has become something of a necessity now that we do the longest working hours in Europe; hours which eat into our social lives dramatically." Whereas work used to be viewed as something very separate to friends and family, these days it often takes centre-stage in our lives, and boundaries get unhealthily blurred.
Claire Langman, 32, joined a retail management scheme at the same time as eight others. "We spent a lot of time together at work and several of us got very close outside the office as well. We were having a great time, then as we came closer to permanent job offers, things got tense."
Two of them wanted jobs in the same department and there was plenty of back-stabbing. "I'm not proud of the way I handled it," Claire admits, "luring others in the group to slag off my competitor. Practically bullying them into joining my gang as it were. It all seems hideously childish now."
According to Judy James, many work friendships have the same effect as a sexual relationship between two colleagues. "They can screw up the dynamics of an office in that they create a similar tribal situation to that which occurs in the school playground." Two people who become close can be perceived as one much stronger unit and create an imbalance that becomes a problem for everyone else.
James also believes we have unrealistically high expectations of work friendships. "Colleagues are thrown together at random, and when relationships don't work out we're puzzled. We must be prepared to lower our expectations to `just getting along'. I believe it's better not to be best buddies anyway."
Dr Yager found that friendships formed at the same level were the safest, and generally led to camaraderie and support. Women bosses are more likely to form friendships with those working for them than men, which can be dangerous - "the wrong person could affect your status," she says.
At the same time, Yager believes women have yet to exploit "befriending up". "Traditionally women have feared befriending a male mentor because of worries of sexual harassment or office innuendo, as men have usually held the positions of power. Men wanting to climb the ladder haven't had that problem; they've accessed the mentor and learnt from them while developing the relationship. Then they move on professionally and keep the friendship."
In the end, Claire Langman lost out on the job she wanted, but she managed to salvage the friendship. "As soon as I heard she had the job I was overwhelmed with regret about the way I behaved."
And what about the person who gets the promotion? Can you remain friends with your old work buddies? Almost certainly not, says Judy James. "I often get asked by newly appointed managers, `How can I still be one of the boys/girls?' You can't. A wedge has been driven between you; you just can't be a manager and a friend."
So you may well be left feeling isolated and lonely - and the same goes if your social life revolves around work and you move to another job. "The chances are you will lose those friends when you leave," says James. "The trick is not to let work become the centre of your universe. And don't put all your eggs in one basket. Underneath the gloss, you may find you don't have that much in common after all. Always try to maintain friends outside the office."
So can a work friend never be a true friend? According to Dr Yager it takes three years to test any friendship and "a workplace friendship won't really have been tested enough unless one of you has to relocate, but be warned; typically friendships at work turn out to be based on convenience."
`Friendshifts: The Power of Friendship and How it Shapes our Lives', by Dr Jan Yager, is published by Hannacroix Creek Books, pounds 17.99; `The Office Jungle', by Judy James, is published by HarperCollins, pounds 5.99.
n Keep friendship and work separate as much as possible.
n Be discreet with your friend's secrets. Avoid gossip at work where possible, especially if it involves information you are privileged to know because of a friendship.
n If you feel compromised by your friendship, discuss it and if necessary withdraw from any situations that might involve a conflict of interest.
n Be aware of your company's policy about friendship; some companies have a pro- or an anti-fraternisation policy about friendships at work or between clients or customers.
n If a work friend asks you a very personal question, don't answer. Try changing the subject, make a phone call, suddenly have something else to do if possible. If not, reply directly with "I can't answer that".
n Never misuse a work friendship for "leverage".
n Watch that you and your friend aren't overfamiliar via body language, voice or language in the office.
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