Exchanges only trade during set trading hours — the LSE runs 8am to 4:30pm UK time on weekdays. Outside that window, news doesn't stop: earnings, economic data and global events still happen, they just can't be traded on that exchange until it reopens, sometimes in after-hours sessions on other venues instead.
That's why a stock can open noticeably higher or lower than where it closed the day before — an overnight gap. The first trades of the day happen through an opening auction, where the exchange collects orders and sets a single opening price that reflects everything that happened while it was shut.
A 4% overnight gap — nothing traded, but plenty happened.
Educational content only. It is not personal financial advice.