Dr Brennan was incensed by Mr Sugar's claim on last week's episode that colleges were places "where dummkopfs come to learn where to make mistakes".
Putting Sugar right on some statistics, Dr Brennan said: "I can only assume those comments were made in ignorance of the reality of modern further education - and in particular of the real experiences of the four million students studying there, and of the efforts of the 250,000 staff who work in FE colleges."
And he adds in a letter to Sir Alan: "My astonishment is compounded by the knowledge that one of your own companies - Viglen - is not only a major supplier to colleges, but actively boasts on its website of the importance of that connection."
Then, really turning the knife, he writes: "It seems quite extraordinary that you would want to risk the commercial reputation of your own business.
The example of Gerald Ratner inevitably springs to mind." Ouch!
So further education minister, Bill Rammell, be warned. You risk Dr Brennan's wrath if there are any cheap bracelets among the gems in next week's FE white paper.
More sugar: Letters 4 Email us FErret@tes.co.uk