Question: Why is will it take so long to build HS2?

The HS2 official website (http://www.hs2.org.uk/) says that one of the reasons the rail line will take until 2033 to complete is because the government needs to submit a bill to Parliament and then get the bill passed. This will take two years. The build is also in two phases. Phase one, the route to Birmingham, will take until 2026 to complete. The discussion about whether phase two can go ahead will only begin in 2015. HS2 is the biggest transport project undertaken for a generation. HS1, from London to the Channel Tunnel took 15 years, from the Tunnel’s opening in 1994 until it began operating in 2009.
Another reason it will take such a long time is because the scheme is controversial. Some people do not want HS2 to be built and the government has to take their views into account. For example, the group Stop HS2 object to the project on environmental grounds. Stop HS2 says that 162 wildlife sites are threatened (see http://stophs2.org/)
HS2 will take a long time to build because it is a very complicated technical and engineering challenge. It is also very controversial and there is a lot of criticism about the plan, so it will take a long time for government to pass the bills that will allow HS2 to be built.