This is to clarify that we didn't have any problem from our London location during the mentioned time period.
We received 404 status code from London location from your hosting provider after 2 redirects. It looks like a momentary issue in your end because the rechecks from other locations were fine which was performed immediately after London check. You would have received the headers information for that failure check in your alert mail itself.
In Site24x7 Webclient you can view the header information in the RCA in Outage tab of the Monitor details page.