The 2011 annual report on NBNK Investments casts further light on the state of the negotiations - since abandoned - between NBNK and National Australia Bank over the purchase of Clydesdale Bank, in the UK.In the report, released on Friday, NBNK's chair and chief executive, Gary Hoffman, wrote that "we undertook detailed analysis of other UK based opportunities, notably National Australia Bank's Clydesdale and Yorkshire banks. "That work and the discussions that followed did not result in a transaction which we would have been able to recommend to our shareholders."Cameron Clyne, CEO of NAB, told an investor call on April 30: "We've never received a formal offer for this bank, we've never rejected a formal offer, so it's not as though we are walking past deals in the last three and a half years. "But, as you [would] expect, there has been speculation over the asset and we have received informal expressions of interest, all of which... [were] very low valuations and also highly conditional, and… very difficult to execute."NAB's board has opted for a version of a "good bank, bad bank" resolution for its loss-making UK arm. NAB will shift £6 billion in troubled property loans to the group balance sheet and Clydesdale will close 29 business banking centres in England, with the bank now focusing on markets in Scotland and northern England.NBNK has since resumed talks with Lloyds Banking Group over the purchase of the "Verde" portfolio of branches that the latter must sell to meet European Union requirements.