With today's announcement that the slot rules at UK airports have been tightened to 70/30 use it or lose it, I believe the recent news regarding Vueling expansion at Gatwick
and the chartering of up to 4 Iberia Express aircraft for BA Euroflyer is in part a response by IAG's need to use more of its slots at Gatwick during Summer 2022.
Will be interesting to see if there are any more route expansions at the airport by IAG in the coming weeks.