It is five years since effigies of Nick Clegg were burned in disgust at the trebling of tuition fees: the moment higher education was meant to become the preserve of the wealthy. Those fears have not materialised. Forty per cent more disadvantaged students enter the best institutions now than in 2011, although the replacement of maintenance grants by loans in the last budget means that the poorest students will leave university with over £10,000 more in debt than the richest.

All the while one crisis has gone comparatively unnoticed: the collapse in mature and especially part-time students. They are the forgotten victims of the changes in tuition fees. Since 2009/10, there has been a 10 per cent fall in full-time mature students, and an even more alarming 48.4 per cent drop in part-time students. The drop is starkest among older students: 240,000 UK adults aged 25 and above began part-time course in 2009, but just 115,000 did so in 2013, as a new report from the Independent Commission on Fees outlines.

Tuition fees are driving this collapse. In Northern Ireland and Wales, which have far more generous fees systems than England, the number of part-time students has not declined at all since 2010. “Whereas young people seem to worry a lot less about carrying the burden of debt, mature people seem to worry more,” Les Ebdon, the Director of the Office for Fair Access, recently told me. “It may well be if you've already got a large mortgage debt that you’re not looking for another debt.” Those already in work who are considering studying part-time face a guarantee that they will pay more tax - £360 a year extra if they are earning £25,000 –if they choose to do so, but no guarantee that studying will lead to them earning more. No wonder they are being put off higher education.

George Osborne talks of his vision of moving to a “higher wage economy”. But while improvement in skills are necessary to lifting productivity, wages and boosting growth, adults are being put off investing in their education. The consequences are particularly deleterious for those from disadvantaged backgrounds, who are more likely to apply to university later and on a part-time basis; the unattractiveness of part-time courses thus imperils social mobility. So it is incumbent on the government to explore whether a more benign fees system for older part-time students could be implemented. A comprehensive bursary system for less well-off adults who want to pursue higher education should also be explored.

As it is older students, particularly those studying full-time, face being hammered further. The news that the £21,000 threshold at which tuition fee loans begin to be repaid is likely to be frozen for five years will make the repayment demands for students more onerous in real terms, and so further deter older students from pursuing part-time courses.

That tuition fees have not put off disadvantaged students from university should not invite complacency. The fees system for mature and part-time students is putting too many off developing the skills they need for the UK to thrive.