I spent yesterday running a sustainability strategy workshop for directors and senior managers of a FTSE100 company. They didn’t disappoint – they challenged, they argued, they what-if’d, they demanded evidence and data – everything you would expect from the calibre of people running such a large, complex enterprise. They certainly made me work for my money.

I’ve learnt through experience to be quite flexible with the programme of my workshops, but despite having given a significant amount of additional time early on to debate the business case for sustainability, it was the subject we kept coming back to, still dominating the discussion during the wash-up at the end.

This doesn’t surprise me as I don’t think most organisations truly pin down the business case as it applies to them. Many of us can recite the list – compliance, reduced costs, recruitment and retention of employees, attracting and retaining customers, new business opportunities along with less obvious examples like resource security and asset value protection – but how do they relate? This is vitally important when you have to, say, decide when should you spend to save and when should you spend to invest in the brand?

Interestingly, those who invest in the brand often deliver cost savings, but those who require a return on investment rarely get the brand enhancement. When Sir Stuart Rose put £200m into Marks & Spencer’s Plan A, he did it to protect the venerable chain store’s reputation as the trusted brand on the British high street and didn’t expect to see that money again. But Plan A has returned the investment and indeed made a profit. Conversely, every business worth its salt is trying to drive down energy, water and waste costs, but few if any of them will get the halo that Plan A gives M&S.

But the important thing is that Rose knew precisely what his business priority was – the brand. Pinning down the business case in that way gave him and the Plan A team the clarity and direction to develop and deliver a highly effective sustainability strategy. And that’s why taking so much time in my workshop to explore the business case was essential to take the programme forward.