Actually, the problem is structural underfunding, rather than Successor/F35 or anything else.
That structural underfunding has led to inordinate effort being made to defer procurements / balance - which never ends well and also leads to disruption in other programmes.
The cause of the underfunding has been a fundamental refusal by HMT, FCO and MoD to understand that the world is not full of fluffy bunnies that can be defeated by sending a bunch of wimmins rights activists (sorry, DFiD international aid) and a point-blank denial that the nice Mr Putin was noting of the sort. All dealt with by the idea that if we hoped hard enough and ignored it, it would all go away and we could go on spending on diversity and skools n'ospiculs without consequences.
The annoying thing is that for the sake of about £3Bn/yr "extra" over the last ten (about 0.5% of overall govt spend on average), much of the current grief would not exist.
People are at least making noises that the 2% GDP is a minimum to avoid opprobrium, rather than a badge of honour, but I'm not holding my breath....