yes they can!
The committee established that "bulk interception cannot be used to search for and examine the communications of an individual in the UK unless GCHQ first obtains a specific authorisation naming that individual, signed by a Secretary of State".
Summarized with "yes we can do that if the right person pushes the right buttons but trust us!".
Thereby misunderstanding the majority of the resistance against this mechanism: that its presence becomes already the abomination because only a slight change in legislation or national emergency level could easily change this "signed" procedure. The only proper protection against this is then by not having the infrastructure at all as it will take a lot of time building one from scratch. It's the same with nuclear weapons as there's only way to make sure one doesn't end up using them in ways that will extract a price too big to pay.for all.