https://weather.metoffice.gov.uk/public/adhoc/covid-19-seasonal-advice-banner-message.js

1"use strict";
2(function () {
3    var mainTag = document.querySelector("header"),
4        messageHeader = "COVID-19 ADVICE",
5        bannerElement = document.createElement("section");
6
7    bannerElement.classList.add("beta-banner-component");
8    bannerElement.innerHTML = '<div class="beta-banner-content container row">' +
9        '<div class="col-xs-12 col-sm-2 beta-sign">' + messageHeader + '</div>' +
10        '<div class="col-xs-12 col-sm-10 row beta-message">' +
11            '<div class="beta-banner-header col-xs-12 col-lg-7">Guidelines for outdoor activities are different across the UK. Please follow government advice for your area.</div>' +
12        '</div></div>';
13
14    if (typeof mainTag !== "undefined") {
15        mainTag.parentNode.insertBefore(bannerElement, mainTag.nextSibling);
16    }
17})();