What happens next?

How to become a tube driver
Recognize the forces working against you.
You'll need to overcome a few factors on your way to becoming a train operator, but the biggest obstacle in your path is a union agreement made in 2008. According to this agreement, the tfl is not allowed to advertise externally and, instead, hires mostly from within the organization.
Other positions with the tfl, like customer service assistant, are open to the general public. The application process varies according to position, so you should research your options on the tfl website.