So it would seem it was due to necessity on occasions,and not by choice.
GWR-God's Wonderful Railway- as their employees called it.

Many thanks for your interest in the apparent change of discharge port from London to Avonmouth which I can only surmise may have been due to port congestion or a labour dispute at London.

I never understood the Avonmouth connection to be honest: It seemed strange to me (back in 1970 onwards) that the port was so busy.....sure, Bristol had depth/draft restrictions by then. But why "Avonmouth-for-London"?
Could it be, I wonder, that the old "Great Western Railway" as was Brunel´s dream, provided good freight-rail links to London? Just a short link from Bristol needed?
I'm sure someone will enlighten us, Liberty Ship Lad.
Cheers

Was that a common occurrence,discharging London bound cargo at Avonmouth,presumably when only "western" UK ports were scheduled?

Sigh Indeed Jadran, a classic merchantman of yesteryear. When working such ships meant interesting ports & interesting cargoes of all shapes & sizes....Unlike the Bulkers & Box-Boats of today.
Cheers.S.

Beautiful 'classic' funnel !!! (sigh)

Very nice photo of a cargo passenger ship with extensive handling gear.