J Walter Thompson's parent network, WPP, has acquired a "significant" minority stake in Hirschen Group, an independent agency group in Germany. Hirschen Group took revenues of €37.3 million (£26.9 million) last year and provides advertising, PR, public affairs, consulting and strategy services. It employs more than 500 people in nine offices since being founded in 1995 by Bernd Heusinger and Marcel Loko. Martin Blach joined as its chief executive in 2005. JWT currently employs 150 staff in Germany.