Following his appointment as head coach to the Russian national team, former Sale head coach Kingsley Jones quickly took advantage of Wiltshire's experience by drafting him into the management set up to help prepare Russia for this summer's Churchill Cup in England and for the Rugby World Cup in September.
Between 2005 and 2010 he was employed by the WRU as its National Fitness Director, then National Performance Manager and finally, as National Sports Science & Performance Manager until 2010 when he left to take up a senior position in Performance Analysis and Management at the University of Wales Institute Cardiff (UWIC).
He takes up the role from July 1 and will bring strategic vision, planning and direction to develop elite performance at London Welsh.
Commenting on his appointment, Wiltshire said: "London Welsh has such a proud tradition and widely respected brand, and it's an honour to be involved with a rugby set up that boasts John Taylor, Steve Lewis and Lyn Jones - men who possess real integrity and rugby knowledge of player and game development.
"I saw the quality of Lyn's work first hand and I am delighted to be supporting an international standard coach.
"The aim of my role is to help drive performance standards and promote individual player development. This will require a lot of hard work from all backroom support staff but with close alignment with the key RFU structures and systems, the necessary improvements will be achieved.
"I look forward to supporting a young and talented squad, and helping Lyn make the changes required to take London Welsh to their next stage of development."