Complex sentence: Rimer opened the firm's London office in 2002 and its San Francisco office in 2012, and has become a leading voice on venture capital in Silicon Valley and Europe, and has been actively involved in various philanthropic and cultural activities.
Split into simpler sentences: Rimer opened the firm's London office in 2002 and its San Francisco office in 2012. He has become a leading voice on venture capital in Silicon Valley and Europe, and has been actively involved in various philanthropic and cultural activities.