I removed:
“function submit_button( $text = null, $type = ‘primary’, $name = ‘submit’, $wrap = true, $other_attributes = null ) {
echo get_submit_button( $text, $type, $name, $wrap, $other_attributes );
}”
from wp-admin/includes/template.php
And the WordPress dashboard now appears to work.
Can someone confirm that I haven’t caused another problem elsewhere?