I was on northbound 1F49 which was on time at Haywards Heath this evening but noticed the indicator on platform 2 was showing a cancellation and delays. I've now looked at RTT which shows significant problems with some Thameslink services, possibly caused by the Blackfriars pan strike https://www.railforums.co.uk/threads/thameslink-overhead-wire-issues-at-blackfriars.273677/ but Southern affected about as badly. What was going on?