Professor Justin Bronk: If we do not participate in GCAP, BAE Systems and the UK as a whole would for ever lose the ability to be end-to-end fighter developers and manufacturers. In that sense, it is absolutely essential if our sovereign choice is to remain in that game. It is the only way to do it.

So one of the big issues is timeframe: if Saudi Arabia were to demand being a full, core partner member, that 2035 timeframe would not be possible, at which point the Japanese would leave the programme.

GCAPに参加しないと英は戦闘機の開発/製造能力を失っちゃうけど
日本は2035年に間に合わなくなったら脱退して単独開発しちゃうから

i.imgur.com/8065b59.jpeg
要求性能と期日は全て日本の言う通りにして

開発費6～7割はテンペスト側で負担するけどしょうがないよね