What is Tony Blair's Windrush?

Now here is a tantalising mystery.

"So mystifying are the former prime minister's financial structures – which involve highly specialised limited partnerships and parallel companies – that the Guardian today launches an open invitation to tax specialists and accountants to attempt to explain the motivation behind such structures. We have published the Companies House documents and other legal papers regarding the structure of the partnerships at guardian.co.uk and invite expert comment via our site.

There is no suggestion Blair is doing anything illegal. But he refuses to explain the purpose of the secretive partnerships."

The Guardian has a contest challenging readers and experts to answer the question: what is Windrush?

One other point - our contacts tell us that Tony Blair's wife Cherie Blair has for some years periodically attended St. Thomas's Church in St Helier, Jersey. Is she there just to feed the ducks? Or is there a more interesting Jersey connection?