Re: 'the Iranian nuclear weapons programme'
Pull the other one, it has got bells on it.
They may not have the ultimate intention of building a bomb, it's almost impossible to prove intentions, particularly in a dictatorship. Which is why intelligence deals with capabilities. They have a rocket program (space or ICBM). They built a secret uranium enrichment site, hardened against military attack, and failed to declare it to the IAEA as they are supposed to by a treay they signed (NNPT). They have been working on precision triggering of explosives, also required for nukes - and I'm not even sure if that has a civilian use. That's also from the IAEA reports. They've also refused to dismantle their uranium enrichment program when offered treaty-guaranteed cheaper nuclear fuel deals from Russia (who're building their reactor), paid for by the US.
So even if they don't have a nuclear weapons program (which they patently obviously do), they've been doing everything to make people think that they have a nuclear weapons program.
There's a theory that the Iranian leadership want the ability to build a bomb, without actually doing it. Then they can have the threat of it, without the consequences, or use it as a bargaining chip for something they want. But if true, that policy is indistinguishable from planning to build a bomb, so the response ends up being the same.
Negotiation is hard when you cheat, and then get caught. It'll be incredibly tough to get a solution to the Ukraine crisis, because Putin has blatantly, and often contemptuously, lied at every stage of the conflict. So no one is going to trust him - which makes it hard to come to any deal.
Iran has a similar problem. No-one believes its denials about its nuclear program because it's broken the terms of its treaty saying it wouldn't develop nuclear weapons, and then says it only broke the treaty in order to develop a civilian nuclear program in secret. And none of the secret stuff was military, honest guv.
Lying poisons diplomacy. If Blair and Bush had said we're going to war with Iraq for reasons of policy there'd have been much fewer problems. There were plenty of justifications to use, but none that would get a UN resolution. Going the chemical weapons route, when there was little intelligence about the state of the program was a huge risk. Everyone knew the UN had only destroyed about 80% of Iraq's stocks in the 90s, and they still had the scientists and knowledge to make more. But basing so much on such limited intelligence, and being wrong, has done massive damage to the credibility of the US and UK. And has buggered-up international diplomacy for at least the 2 decades.