I don't think there is any comparison to be made between Tony Benn's arrangements made regarding what would happen to his estate following his death and the the setting up of a company which enabled clients to avoid paying UK tax. As others have said, Wills that are made in this country are public documents, copies of which can, for a small fee, be obtained and examined by anyone. Whilst there was knowledge of David Cameron's father's business, it is only through the leaking of the Panamanian documents that the complex nature of the business and the amount of time during which no tax was paid came to light.
The Guardian reported that David Cameron's father ran an off shore fund that avoided ever having to pay tax in Britain. This was done by hiring a "small army" of Bahamian residents.
"The fund managed tens of millions of pounds on behalf of wealthy families ... The Panama papers reveal the details of how Cameron Senior sheltered Blairmore's profits with a series of extensive and complicated arrangements" [the company was incorporated in Panama but based in the Bahamas]. "Blairmore is shown to have been controlled using an obscure financial instrument known as "bearer shares". These do not carry the name of the owner. They are similar to bank notes in that they simply belong to the person holding the certificate in their hand... In order to avoid UK tax, the venture had to be managed and controlled from abroad. A team of six other directors from Switzerland and the Bahamas was recruited, to ensure that the majority of the Board was based outside Britain. However, the paper trail suggests this was a conjuring trick, albeit one tolerated by the law...."
Whilst I think it is clear that, in the light of all this, DC had no right to take the moral high ground and castigate Jimmy Carr for his arrangements (and he was very selective in his criticisms - making excuses for Gary Barlow), I agree with those who say that this isn't about individuals - it is a systemic, worlwide problem. I think there is a danger that after all the hoo ha has died down, everything will continue as before. Pillorying one or two individuals is not the answer - shutting down these tax havens is. I don't know how it can be done but unless it is, with the gap between rich and poor widening each year, the world will become an even more dangerous place than it is at the moment.