Because DMGT’s “A” ordinary shares do not carry voting rights, they will be classified from 31 May 2012 (when the listing regime changes take final effect) as having a “standard” listing for the purposes of the UK Listing Authority’s listing regime.
As a result, the “A” shares will be not eligible for inclusion in the FTSE UK index series – as shares with a “standard” listing are not included in the FTSE indices.
See this RNS from DMGT (which states that DMGT will continue to apply the UK Corporate Governance Code, although that is not a requirement for standard listings) and this FTSE announcement.
The UKLA’s explanation of the listing regime is here.