I wrote a couple of weeks ago about the problems on some train lines in and through London.

These have not been resolved and so National Rail has told the train operators to ‘declassify’ First Class during week day peak travel hours. This means that you can sit in a First Class seat with a standard class ticket and not get a penalty. Only applies as follows:

Based on when the service departs the station; Monday to Friday:

• The AM peak is from 06:30 to 09:30
• The PM peak is from 16:00 to 19:15.

With immediate effect (until 15 July), all first class on Thameslink and Great Northern services will be declassified in the am and pm peaks only. The interim timetable is launched on 15 July and first class will be reinstated then.

As I mentioned before there is greater flexibility on ticket usage:

Season, single and return tickets printed with ‘Thameslink Only’, ‘Southern Only’ or ‘Not Gatwick Express’ can be used on any Gatwick Express, Southern or Thameslink train service to enable you to complete your journey.