The question 'What's the blueprint for the ideal senior interim HR professional?' provokes a similarly complicated answer. It's a wish list dependent on the job to be done, the company, the culture, the economic climate, the timeframe, possibly even the weather. But just as the pie is common to all of Sally's idiosyncratic dessert options, there are characteristics that all successful HR interims - those who come into a business temporarily, often to manage a change - share.
"Any interim manager has to effect change in a very short space of time - a much more accelerated period than if they were permanent," says Doug Baird, MD of interim provider Interim Partners. "They need to start defining the relationship and the timetable immediately."
Jason Atkinson, MD of fellow interim provider Russam GMS and chairman of the Interim Management Association (IMA), agrees: "They have to be able to come in, engage with key people, diagnose the root cause. They may have to go to the client within the first five days and say: 'You thought the objective would be this but actually, I think it might be this'."
Experienced interim HR practitioners confirm this. "You have to be able to go at a certain pace. You've got to go in, decide what the issues are, what you're going to do about them, and do it," says Gary Fisher, director of HR consultancy GEFConsult. He has 30 years' corporate HR experience, including working as, and hiring, interims. "When I have hired interims myself, there have been a few who weren't working at the pace needed and I have had to remind them: 'Hey, you're only here for a short period and we need to get the job done'."
While interim managers do increasingly offer the kind of strategic advice usually associated with consultants, this ability to roll up their sleeves and get stuck in is crucial. The lines may be blurring, but only those up for the hard graft should consider it.
Atkinson highlights other shared traits, including the ability to form relationships quickly, the power to influence and motivate people at all levels, leadership skills and a certain maverick confidence. "We do behavioural analysis and an entrepreneurial, visionary approach is common," he says. "Whether an HR expert, or finance, or any other type of interim, good interims look for new ways to do things. They're stubborn and opinionated, but they know where to draw the line."
So, with basic characteristics established, is it better for an interim HR professional to be a generalist or to have a specialist skill around, for example, benefits, recruitment, talent management, legislation or redundancy? And does international experience add anything to the mix?
Interim providers agree that around 80% of interim HR assignments focus on change - restructuring, cutting costs, or integration - and require a broad range of skills. In many SMEs, generalists are most in demand, but in larger operations, requirements are changing.
Five years ago, says Atkinson, a senior interim HR was likely to be a Jack or Jill of all trades - an ex-HRD who could do it all. "Now, with very few HRD roles around, a CV has to say 'expert in comps and bens, OD and so on', offering specific sought-after skills," he says. "Specialism is the name of the game for the future."
Baird believes industry-specific experience is also a benefit. "An expert HR practitioner experienced in a particular sector will gain a lot more credibility with employers in that sector," he says. "Nowadays, there are more candidates, so clients have more choice and can be demanding."
And across the board, demand for interim managers is growing. Research by the IMA reveals there has been an increase in interim assignments every quarter since Q4 2011.
Specialisms in demand vary, but include up-to-date knowledge of legislation, particularly around recent changes in rules surrounding 'controlling persons' - benefits, health and safety, union issues, employment rights. Experience in another discipline - problem-solving or project management or finance, for example - is also an asset. While international experience can be valuable in handling multinational assignments for large corporations, there is a general consensus that such experience is not an essential.
Unsurprisingly, it is the extra knowledge that interims bring with them that often proves most valuable - not just around the subject at hand, but the wider business and economic climate. "HRD interims really need to be up-to-date on things the business may not be so sure of," says Baird. "These might not even be the key aspect, but would really be significant, certainly in the public sector."
And the 'most wanted' specialist skills are shifting to reflect the economic climate. Chloe Watts, head of HR practice at interim provider Alium Partners, predicts more demand for interims with mergers and acquisitions experience as the economy improves, and also recruitment. "We have seen more of this in the past six months than in three years," she says.
Another skill that is being requested more often, says Watts, is the ability to forecast the HR implications for tenders. "More interims are being required early on in the process," she adds. "Looking at it from a people perspective and the costs and likely outcomes, pre-bid, could mean avoiding a non-profitable deal."
The necessary combination of skills, experience and gravitas means an effective interim has to have notched up a certain number of years at senior level. However, the average interim is no longer a white male in his late 50s or 60s. The average age - particularly in HR - is falling, say most interim providers, and women are now much more widely represented in HR.
This reflects the fact that the impetus for a career in interim management varies. Some make the move after they finish their in-house careers. For some, it is a decision born from a change in circumstances. For others, it is a conscious step on a strategic career path.
However, it is surprisingly flexible. Russam GMS's latest snapshot survey of the interim market in the six months to June 30 2012 reveals that, while 27% of interims would "never take a permanent full-time job", nearly half (49%) would, with 8% actively seeking one. A total of 39% would "happily move between the two".
But whatever the reasons for entering the market, how does an interim wannabe prepare themselves to take the plunge?
"One of the potential pitfalls is to have no focus," says Baird. "You can spot the interims who are unprepared. They need to set up a limited company with a full business plan, get insurance, and exploit their network. They have to see getting their first assignment as a full-time job. And they can't be as choosy as they might like."
Fisher's decade as an interim followed 20 years in corporate HR, and such is the demand for his services that he now has three associates. But, he says, getting started was hard work: "I made a definite decision to start my own business as an interim after being made redundant but, at the time, I don't think I realised the full implications. I did a business plan identifying four different potential revenue streams and I networked widely. It was a bit like sending out helium balloons and hoping someone would grab hold of a string."
Alium's Watts believes that, while new interims might have a sound grasp of the practical issues, they also need to be aware of the potential emotional upheaval: "What people do miss is a sense of belonging. They lose their peer network and they can't get this in the client's organisation. They need to build a strong network of professional peers."
Baird also advises taking a different perspective on interviews for an interim role and brushing up on sales skills: "Treat it as if you were selling a business proposition or service, rather than as an employee," he says. "Take a diagnostic approach, and say: 'Let me see if I have the necessary skills to help you'. Make your enthusiasm for the assignment clear to the client. Learn to close. And all the time, highlight the skills you can provide to offer a solution."
Get under the skin of an organisation quickly: an interim's view
Daksha Mehta got into interim work almost by accident. The senior permanent role she was in evolved into one where she was being asked to step in as a 'troubleshooter': taking on specific projects in various sectors and locations. It began to resemble an interim role, and Mehta found she enjoyed this way of working.
"I like the fact that you have to do everything at speed," she says. "You have been brought in to solve a problem. It's exciting. You have to get under the skin of an organisation quickly and take on the brand, culture and issues within days."
She decided to branch out on her own and now works for about nine months of the year, selecting her assignments carefully. "You have to be interested and enjoy being with the people immediately. In a permanent position, you can take some time to find your way; as an interim, you need to do it at once."
Most of her assignments have centred on change management, particularly integrating a new acquisition. Others have been more strategic, but all have required a range of skills. "When I am getting ready for a new project, I work day and night researching its specific issues and concerns," she says. "I am constantly researching and updating my knowledge, so I am thinking: 'This is how I normally do it, but what else is out there?'"
The key for Mehta is being able to make a difference quickly. "An interim thrives on that," she says. "It's a bad assignment when you know you're not being used to your full potential. ?I have only had one that I wasn't particularly keen on. I think I decided a bit too quickly and went for the brand. They brought me in for a specific role and then politics came into play, as someone internal wanted that piece of work.
"I was left with a normal organisational role and it took me a month to say: 'Look, this isn't working…' If that ever happened again, I would go a lot sooner."