There is a Phase banner component implemented in the gds/base.html
template that is include in the template pack. It is wrapped with a {% block %}
tag so if you extend the base template you can override it if you need to.
Within the {% block phase_banner %}
tag there are two daughter blocks: {% block phase_banner__tag %}
and {% block phase_banner__text %}
so you can selectively override these if you don't want to override the entire phase_banner block.