On "shrouds of secrecy" and political will
Here's an extract from a letter David Cameron sent to the British Overseas Territories - 'our' tax havens - in April 2014:

Well put. Sunlight is the best disinfectant. "Tax evasion and illicit finance" are scourges. They need to be addressed, and "urgently". And transparency is "vital" to meeting to those challenges.
As a BIS paper produced under the Coalition put it (in respect of plans for our own registry):

And as Cameron reportedly said, speaking in Singapore this July:

Having made a world-leading commitment to tackle these issues you'd expect the Conservatives to remind us of it in the run up to the General Election. And, amid the febrile atmosphere surrounding the HSBC disclosures of thousands of wealthy tax evaders and one prosecution, they did. Cameron demanded that British Overseas Territories publish plans to create central register revealing companies’ ultimate owners by November. This month.
Of course, the General Election has now come and gone.
So how now press upon the Prime Minister the concerns that so troubled him then?
What's happened?
In response to a written question from Margaret Hodge, James Duddridge, the Parliamentary Under-Secretary of State for Foreign and Commonwealth Affairs yesterday said this.

Or, in a word, nothing.
The UK does possess the power to force our tax havens to adopt this measure - at least that's what an article in the highly respected New Law Journal concluded. It's just a matter of political will. Which seems to be in rather shorter supply after the General Election than it was before it.
When, back in March, Cameron renewed his demands to the British Overseas Territories, the International Financial Centres Forum - a lobby group for British Overseas Territories - said the demands were "clearly politically driven given the timing."
Sadly, events have shown it to be right.
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Thanks to @davidtpegg for alerting me to the James Duddridge statement.