Some further thoughts -
1. The city government of Liverpool was known, until the 1970s, as "Liverpool Corporation." So while Americans hear "corporation t-shirt" as a reference to business corporations (I know I always did), Britons may be quicker to associate it with the municipal authorities.
But what would "corporation t-shirt" mean? I'll get to that in a minute.
2. The song is full of John's grief over his mother's death, together with his fury at what he and his family believed was a cover-up of a policeman's drunken negligence.
The family, including John, attended the inquest into his mother's death, where they would have seen policemen "sitting in a row" and heard the driver's self-serving testimony. "See how they sny like pigs in a sty"? Try substituting LIE for the meaningless "sny." Of course any "smiles" from the pigs in a sty would have added to John's (and Mimi's) fury.
3. The dismissive "expert textpert" refers (I contend) to the "expert testimony" that would have been presented at the inquest regarding the speed of the fatal vehicle, the difficulty of braking when Julia stepped off the curb, etc. It's one thing for the driver to lie. But tendentious testimony from experts would have shown that the fix was in at the institutional level.
4. How about "corporation t-shirt"? I propose that John really wanted to denounce the "corporation bull sh*t" -- i.e., the B.S. from the municipal authorities. But he but censored himself by switching to the similar-sounding but nonsensical "t-shirt". The testimony, the inquest and the verdict ("misadventure") were a lot of bull sh*t.
5. Now consider the famous line about "see how they fly, like Lucy in the sky." The witnesses are agreed that the impact sent Julia flying HIGH IN THE AIR before she hit the pavement (100 feet down the road, according to one account, although that seems exaggerated). True, John didn't write "see how SHE flies." But he didn't want people to know what he was actually writing about, so switched the pronoun (also helps the rhyme). Of course, the beginning of the song ('I am he,' etc.) demonstrates that John was willing to jumble pronouns with abandon. Even with the pronoun changed to "they," the presence of "Lucy in the sky" preserves the essential image -- a woman flying through the air.
6. Mimi, hearing the impact, ran out of Mendips to the scene of the accident. She stayed with Julia, distraught, until the ambulance arrived. As in "waiting for the van to come." What about "sitting on a cornflake"? It's silly. But could John have been referring to Mimi sitting on/at the "corner"? Or "sitting on the pavement" or something like that?
7. All in all, John kept a stiff upper lip following the significant deaths in his life (Mimi's George, Julia, Stu Suttcliffe) -- he didn't "let his face grow long" (which would have made him a naughty boy by Mimi's lights). In the song, though, John finally gives voice to his private grief ("I'M CRYING").
8. Biographers also recount that John responded, initially and in private, with "hysterics" - crazed, cackling laughter -- to the death of George and Stu. I don't know about his private reaction to Julia's death, but I am certainly reminded of the crazed, cackling laughter that you hear on "I Am The Walrus."
9. On the other hand, what about the line "Don't you think the joker laughs at you" (which sets up the crazed laughter)? Here I think John is expressing his scorn and contempt for the "texpert" and the rest of the dishonest inquest.
Of course, John later told interviewers how random the song was, how he really just wanted to put one over on the oh-so-earnest literary types, etc. And I do think that he stuck in plenty of nonsense to throw us off the track.
But basically John was singing about what may have been the most traumatic event in his life -- and the music fits perfectly. But he didn't want us to know it (too personal, too intense), and he didn't want to go on record in 1967 with a song expressing such angry contempt for the Liverpool police.
Thanks.
[disregard this: score minus one nachtigal]