Only partly right Three of those diversions were UK domestics and landed at SEN well before the LCY curfew.
Whatever the reason it would seem that while LCY was slot restricted SEN was not, so the airlines were able to plan those flights into SEN.
Now that SEN has its own CTA/CTR that is contiguous with the LTMA presumably SEN arrivals from the north can avoid the need to work Thames Radar ?