Special mention to Thomas Cochrane and Sir Marc Isambard Brunel & his son Isambard Kingdom Brunel who built the Thames Tunnel.
Constructed between 1825 and 1843 it wasn't just the world's first underwater tunnel, but the first to implement a tunnelling shield - the basis for all TBM's (tunnel boring machines) to this date. The 25th March represnted the
168th year since opening and is now the core section of the East London Line.
Source: murphyz at Flickr.com
Another mention goes out Colonel G. T. Landmann who was the Royal Engineer behind the London and Greenwich Railway. Constructed between 1834-36, the line was the world's first elevated railway, with the world's first train city centre train terminus (London Bridge Station).
The elevated route spans 851 arches and 27 skew arches (5.5km) and at its widest point accomodates 12 tracks. Despite being
175 years old, the route is still in use by hundreds of trains each day. I'd be interested to know how many millions (perhaps billions) of bricks were used to construct the route.
Source: Neil Pulling at Flickr.com
Source: turner.adam at Flickr.com