Higher education is a multi-billion pound industry and the stakes are high for attracting students and landing research contracts.

So it should come as no surprise that university principals get six-figure salaries that far exceed the average wage in Scotland.

However, the quid pro quo should be that the individuals who benefit from big-league salaries should devote all of their professional energies to the job.

Sir Jim McDonald is Strathclyde University’s homegrown principal. He has a connection to the institution going back decades and he was appointed to the job in 2009.

As we revealed last week, Sir Jim’s remuneration package jumped by 5% last year to £360,000, which makes him Scotland’s highest paid principal.

However, he has also found enough time in his schedule to take several outside appointments that top up his huge salary.

Not only is he on the board of engineering giant the Weir Group - where he earns around £57,000 a year - but he is also a non executive director of a renewable energy firm.

As we reveal today, he is also the chair of the audit committee at Scottish Power, but it is unclear how much he earns from the firm, or how many days he works there.

On the basis of a conservative calculation, which excludes the Scottish Power role, Sir Jim can expect to take home another £70,000 on top of his University salary.

At the very least, University principals should provide answers about the income received, and time spent on, outside jobs.

As Vonnie Sandlan, the president of the National Union of Students in Scotland, put it: “We must question how much time any outside interests take up, the pay and benefits they receive from these endeavours, and, perhaps most importantly, how much the institution and students within it benefit from the principal’s external activities. It’s vital that we have full transparency about the second jobs and outside interest of those leading our publicly funded institutions.”

Public bodies, including universities, have been forced to keep a lid on pay rises in recent years due to funding squeezes.

And although Sir Jim’s remuneration package increased by 5%, it should be pointed out that his salary only rose by 1.1%.

However, pay restraint is irrelevant if the most senior figures in an organisation secure extra money through corporate board positions.

Principals should have one job: the role they are being paid to do by their University.