Environmentalists have staged various attempts to disrupt the approved portion by blocking construction access and in one case, even placing protestors inside the already built pipes.
The debts incurred in the construction of the stadium mean that events need to be staged at Wembley on a regular basis to ensure a steady stream of income.
Particular scrutiny is being paid to the construction of the Maracana Stadium in Rio de Janeiro, which hosted the final the last time Brazil staged the World Cup in 1950 and is due to reopen with a match against England on June 2.