It has got so much more stressful since 911. In the 90's I flew a lot to the US, Australia and around Europe and it was very easy. I then flew into Washington Dulles 2 weeks after 911. OMG, that was horrible. Massive queues at passport control and a huge number of untrained, highly aggressive...
I don't qualify for MI6 because all the passports are in the same name.
Interestingly, or maybe not, i was interviewed by an MI6 handler once without me realising I was being interviewed/assessed for possible recruitment. I failed and I didn't even know until several years later.
I got a letter from my employer stating that I travelled often to countries where a visa has to be obtained in advance and they quickly issued a second passport. I've been to Ireland once, a few years ago. If you have an Irish grandparent you can become an Irish citizen and get the passport. I...
Maybe not. When I renewed my driving license 3 years ago they told me there was no need to send a photo because they had online access online to my passport photo and would use that.
I have 3 passports; 2 UK ones, so that I can still travel when one is away to get a visa inserted, and an Irish one so that I can continue to be an EU citizen.