What's the best way to whiten towels?

[Aquicknamechange2019]

My white towels and flannels are looking a bit grey. How can I whiten them again?

Vanish whitening powder and a 90 wash with bio washing powder/capsule.
If that fails - treat yourself to some new ones in the sales!

Vanish and hanging outside in bright hot sunshine.

Sun is an amazing brightener. Going to have to wait a bit though!