Financial details were not disclosed.

The arrival of Kadens comes after Hamburg's private investment firm Genui also took a strategic stake in the ESG specialist and energy optimisation expert.

According to Westbridge, the new shareholder provides the firm with direct access to international markets, with the Kadens platform and broad investor base opening new opportunities to directly connect to real estate markets outside of Germany. The addition of Kadens to the company’s strategic shareholders thus represents another important step forward in Westbridge’s strategy for international growth.

Matthias Cordier, founding partner of Kadens Capital, said: 'Ever increasing regulatory pressures and the growing need for carbon-free energy sources make complex sustainability services to the real estate sector a long-term growth market, both in Germany and internationally.'

Rüdiger Salzmann, managing partner of Westbridge, added: 'The entry of Kadens as a strategic investor is a milestone for Westbridge and shows that we are on the right track.

'Our commitment and heartfelt devotion to ESG and energy optimisation as well as our capabilities and expertise across its many complex facets, has put us in the unique position of being able to provide our clients, whether within Germany or beyond, with fundamental value added through sustainability.

'Against the backdrop of the continued roll-out of our extensive range of services, particularly for the residential construction sector, and the ongoing internationalisation of our company, we are better positioned than ever as leading sustainability expert to the industry.'

Added Cordier: 'We see our commitment to Westbridge as a clear win-win situation for both sides. Westbridge can make full use of the Kadens platform and international network to develop valuable contacts with a view to expanding its business internationally.

'On the other side, we are able to secure direct access to market-leading expertise and comprehensive practical know-how in all matters of sustainability, which is of great interest to our international investor base.'

Westbridge is currently in the process of merging with ESG peer Argentus and also recently took over Agradblue, a climate protection specialist. The new combine will create one of the biggest ESG-focused advisories in Germany, with around 150 team members.

The managing directors of Westbridge are Christopher Feliks, Patrick Kämpfner, Yama Mahasher, Rüdiger Salzmann and Simon Szpyrka.