Good news: FT-450D is not faulty.
Bad news: I shall be surrendering my intermediate and full licences immediately 😂

For those who haven't seen an earlier reply, the fault has been found.

There was a high impedance air gap between transformer and antenna element. Ergo, the element fell off the impedence transformer!

I feel like such an idiot!

@G8RKE Life happens… I blew up a $150 RF amplifier twice! (… and installed the replacement part in backwards >> SMOKE on power up.) Eventually got it working again. All part of the hobby… 73
@n8dmt Indeed! Downside is I now have one less excuse to buy new one!