oliverdavies.uk/source/_partials/title.html.twig

{% set separator = '|' %}
{% spaceless %}<title>
    {% if page.full_title %}
        {{ page.full_title }}
    {% elseif page.title and site.title %}
        {{ page.title }} {{ separator }} {{ site.title }}
    {% elseif site.title %}
        {% if site.subtitle %}
            {{ site.subtitle }} {{ separator }} {{ site.title }}
        {% else %}
            {{ site.title }}
        {% endif %}
    {% endif %}
</title>{% endspaceless %}