It's been nearly 36 years -- so let's confess. Diana's wedding dress was badly designed.
The whole thing was massively overblown. Apparently, knowing that millions of TV viewers (more than three-quarters of a billion, as it turned out) would have to tell her from the guests and from her groom, for that matter, the designer thought that her train should be 8 miles long and the gauze veil over her -- emphasizing her chastity? -- should be fountain-like in its volume, and that her sleeves should be layered and large enough to accommodate the biceps of an Arnold Schwarzenegger. Viewed from a certain perspective, the dress was a typically 1980s botch. Her bouquet was less a posy than an escutcheon, reaching down her dress in almost Little Shop Of Horrors fashion. It was a dress that seemed to emphasize her shoulders, while leaving her lovely neck bare of ornament -- and all at the expense of her chest, which no one was invited to notice. The rest of her was rendered as a triangular meringue. In short, the dress was fussy, frilly, unflattering, and out of proportion. Why did no one see this at the time?
Well, some did. As one Canadian journalist wrote just after the event, 'only a monster would suggest that the dress was too much'. Well, I am not a monster as my loved ones will attest, but when your fabric shoulders are broader than your groom's -- even with his uniform on -- you can be sure that your dress is far too much. No wonder she thought there were three people in her marriage: she began it by wearing enough for two of them!
Edit: In looking for another photo to show the enormousness of the gown -- is this a dress or a daybed? -- I saw this comment on Wikipedia, quoting an observer: 'the dress was a crinoline, a symbol of sexuality and grandiosity, a meringue embroidered with pearls and sequins, its bodice frilled with lace'. So I'm not the only one to think of the dress as a meringue, then!
The lace, by the way, was hand-made and had belonged to Queen Mary. Possibly it had been worn as an adornment in a way that is utterly foreign to modern fashion, which is why it could be used to a new purpose without apparently despoiling any antique clothing. In Police At The Funeral, a 1931 detective mystery by the English writer Margery Allingham, we are told that the octogenarian matriarch had a closet full of lace, which she wore in rotation so that no one in several weeks would ever see the same lace on her twice.