Complex sentence: Greenwich Council started work to upgrade the tunnel on 19 April 2010, intending to reduce leakage, improve drainage and install new lifts, CCTV, communication facilities and signage.
Split into simpler sentences: Greenwich Council started work to upgrade the tunnel on 19 April 2010. The works will reduce leakage, improve drainage and see the installation of new lifts, CCTV, communication facilities and signage.