My data compromising of 30 firms from the FTSE 100 suggests that this would have little to no impact on English directors, especially those on banking boards. Anecdotal evidence suggested that where directors hold more than three positions most of those positions are held on boards abroad rather than in the UK.
As for multiple directorships or interlocks on banking boards it seems such a proposal will have little impact on UK banks. For example, The Royal Bank of Scotland's (RBS) executive directors in 2006 held between them three multiple directorships with a total of seven executives serving throughout that year (0.42 directorships per director). For 2010 there were no multiple directorships held by any executives throughout the year.
Non-executives portray a potentially different story; but again using RBS as an example throughout 2006 eleven non-executives served on the board with a total of twenty-seven other directorships held between them (2.45 per director). In 2010 however, ten non-executives served throughout the year with a total of sixteen other directorships (1.6 per director).
Although interlocks are unsurprisingly higher for non-executives and not uncommon amongst executives (although RBS is perhaps not the best example of this) neither seem to trouble potential thresholds suggested by the EU.
However, just because UK boards rarely break the suggested thresholds one would still not support a cap on interlocks. Boards need to be dynamic to respond to changing conditions and trying to straight-jacket boards is not a feature of a modern economy.