London, Aug 17 - Hollywood star Brad Pitt is all set to star as Sherlock Holmes' arch enemy, Moriarty, in Guy Ritchie's forthcoming film.

Pitt, who had also starred in the British filmmaker's 'Snatch', had a couple of days free in his busy schedule so he gave his nod to play the evil criminal mastermind, reported mirror.co.uk.

Filming with Pitt is due to start this week in London and on location at Cliveden House -- the venue beside the Thames at Berkshire is the backdrop for Moriarty's home.

'It's a huge coup to have Pitt joining the cast. He has worked for Guy Ritchie before and said if he could, he would do anything to help out,' said a source.

'Pitt is expected to be filming all over London. Cliveden House has been earmarked as a location for Moriarty's home. There will be scenes shot at Royal Victoria Dock, Pontoon Docks, Pinewood and Chatham Docks in Kent. And they will be using clips around City of London to set the scene.

'It's going to be a full-on couple of days, but now the release date has been pushed back they might just do it in time,' added the source.