Near 25,000 crowd - first home defeat of the season, followed as it happened by a second in the next home game.
Headline grabbing opponents on their way to going one better than Argyle's achievement a generation later, their fate sealed by a future Argyle manager but not at the church on the Parade!

Any offers?

Church on the Parade....St Andrews, so there's a Birmingham City connection..

The home defeats.......Norwich City followed by Accrington Stanley in 1959 ?

Humphry Davy has a connection with Sunderland...

Any more offers?

I think this one is just about sorted!

1958-59, St. Andrews - yes
Sunderland, Birmingham City - no

I'm thinking Peter Reid for the future Argyle manager as he played against Watford in the 83/84 final..?

Not Peter Reid I'm afraid, but stay with the Cup theme.

Don't know if this is the full answer but Norwich got to the FA Cup semi-final as a 3rd tier team in '59 same as us in '84. They went one better in taking it to a replay against Luton at St. Andrews before losing to a Billy Bingham goal.
That season (58-59), we suffered our first home defeat of the season against Norwich followed by Accrington, as mentioned earlier.

Is there a Swindon Town link?

There could be some light at the end of the Argyle tunnel as Humphry Davy invented a light.

Don't know if this is the full answer but Norwich got to the FA Cup semi-final as a 3rd tier team in '59 same as us in '84. They went one better in taking it to a replay against Luton at St. Andrews before losing to a Billy Bingham goal.
That season (58-59), we suffered our first home defeat of the season against Norwich followed by Accrington, as mentioned earlier.

Sounds like the answer to me.

No idea where Humphrey Davy reference fits though?

lipsonlad67 has indeed done the business on this one! Before rounding it off would anyone like to have a go at the Humphry Davy link which perhaps, on relection, does not deserve to be called a clue!

SG

All i can offer is Davy invented miner's lamp. Previously Canaries were sent down mines?