AP4 petitioning started yesterday, and will continue until 13th November. Meanwhile AP3 petitioning continues until 23rd October.
If you are affected by the changes in AP3 or AP4 you can petition the select committee.
More details can be found on the Government’s website here
And here’s what Camden Against HS2 had to say about AP3. AP4 and the associated Supplementary Environmental Statement also affects areas along the entire line between London and Birmingham