The Dartford crossing, Which cost more to build?

Question

Was it the Queen Elizabeth II Bridge

or

The tunnels

Answer 1

The bridge. (but inflation means a £ when the tunnels were built is worth more in real terms than a £ when the bridge was built).

Adjusting the cost of the bridge to allow for inflation is what you need to do, in order to compare with the tunnels.  And since there are two tunnels, you need to adjust to allow for inflation twice:

1st tunnel - cost +

2nd tunnel - cost adjusted for inflation

vs

bridge - cost adjusted for inflation