Who decides who makes the announcements?
 

On some recent flights with a large UK-based airline we got the usual introduction/route/height etc announcements from the FO in both cases. On another airline it was the captain both times, and I've had cases of captain out, FO back and vice versa.

So who decides, and how?
Company procedure?
Rock-paper-scissors/coin toss?
Mutual agreement as to who has the better microphone voice?
Captain pulls rank?

This is intentionally light-hearted but I'd be curious to see how this gets resolved.

In my old airline, it was always the captain who made the welcome PA, as a matter of courtesy. After that, it was the pilot operating the sector. One strange thing I found with some of the new F.O.s was that while they were happy on the radio, speaking to anyone listening within a hundred miles or more, they were reluctant to do the PA to a few dozen passengers.

Just a quick aside if I may. Whilst we were in the departure lounge at Houston many years ago there were lots of tannoy announcements asking individual members of the public to pick up the nearest white phone etc. In amongst all the announcements was one for 'Mr Pickle, Mr Dill Pickle please pick up the nearest phone etc'. We listened quite attentively after that to weed out the real ones from the fake ones. Maybe bored staff or someone trying to win bet of some sort!

Not saying that this was the case here, but airport PA announcements may be coded messages for staff. Such as "Mr. Pickles and party please report to Gate 18" can be code for security personnel to get down to Gate 18 to deal with an unruly passenger. Or "Mr. Chutney and party please report to Gate 18" could be code for medical personnel to get to Gate 18. The goal of all this being to avoid alerting the miscreant or alarming other pax. Note that for coded messages to be effective, the name cue (Mr. Pickles or Mr. Chutney) must be both memorable and uncommon. Using Mr. Smith as a code call is not wise.

That could actually be a real person (or persons). If you're not familiar with UK politics, google or Wiki Eric Pickles.

Not at my airline, and not at any I've flown for, so not as universal as it may sound.

At my airline, the Captain will do the Welcome Aboard PA unless delegated to the FO. The delegation is usually done nearing upgrade time or on the taxi. While in flight, the Pilot Monitoring completes all subsequent regular PA's. This is to avoid having to transfer control of the aircraft to do a PA. It's easier to hand off the radios to the PF and have the PM "go in the back."

Our training department and ops manuals strongly suggest that the Captain complete any abnormal or emergency PA, regardless of their duties for the flight. As an old chief of mine used to say "In the moment, the passengers want to hear the voice of God; not the recently or soon-to-be departed." I always thought that a little extreme a saying, but it kind of got the point across.

It could be, but you quoted the announcement as Mr. Dill Pickles, not Mr. John Pickles.

No. I quoted the supposed announcement you posted, i.e. "Mr. Pickles and party".

The captain decides just like everything else. At my old airline the captain usually made any welcome aboard or announcement about delays. We usually flew every other leg, and the pilot not flying did the talking both on the radio and the PA.

Nah, Wilfred Pickles.

He was rather before my time, sadly...