According to a BBC statement his non-involvement is �due to a clash of filming dates� following �several offers for parts in US pilots�
�It is a shame that, due to his current filming commitments, Adrian cannot join us this time round but his new projects are a great testament to his talent and the success of Hustle in the US.�
His character - Michael Stone - wil lbe away doing a long con in Australia, so he could perhaps return next series.