The increasing internationalisation and globalisation of business has meant that accounting increasingly is crossing national boundaries and that it has heightened importance to national and international users. This has highlighted the problem of how best to compare information created in different languages, currencies and formats, in a way that accords with different generally accepted accounting principles and yet also reflects economic, social, political and historical environments. In this paper we analyse the Annual Report and Accounts of companies belonging to the FTSE 300 index in order to draw conclusions about the current state of efforts directed to international harmonisation of accounting standards. We introduce a new method of measuring harmonisation that combines harmony index analysis with the calculation of the index distribution and probability of obtaining higher values. This methodology is applied in measure of de facto harmony for major areas of accounting diversity. The results allow us to identify areas of 'high', 'medium' and 'low' harmony. The highest levels of harmony are observed in the translation of foreign financial statements and in the recognition of acquired intangible assets. But more importantly, our measurement method is a useful diagnostic tool for it identifies low levels of harmony, which ought to be the focus of attention by those responsible for effecting accounting harmonisation. We observed the lowest levels of harmony in the recognition of temporary differences in deferred taxes and measurement of inventories.