HSBC had a lot of customers in Switzerland with secret bank accounts, and it helped them and conspired with them to break British law. Even if HMRC does not want to do anything about it, it seems to me that it was obtaining financial advantage by deception, which is a general crime, not something that needs to be prosecuted by HMRC.
Why are the names of these self-confessed tax swindlers kept secret? The names of small businesses that get into trouble with HMRC—it is worth bearing in mind the fact that that organisation puts more companies in this country out of business than any other—are not kept secret, even if all that happened was that they could not keep up their tax payments: they have not been doing any fiddling or swindling, or breaking the law.
I want to move on to the much wider question of whether the HSBC subsidiary in Switzerland was the only offender. HSBC has 556 subsidiary companies located in tax havens. Why are they there? It might be because of the weather in some tax havens, but not in all of them. Was the Swiss racket a one-off? No answer. Barclays has 390 subsidiaries in tax havens and RBS has 406, while Lloyds, to be fair, has rather fewer with just 297.