I mowed the front today with the new oil and it performed its task without complaint. I managed to fit a Victa axle retaining clip to the front axle and made up a shim from a piece of scrap tin as non of the Victa ones would fit. It looks to be effective enough.
See pics below.

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IMG_20190925_162324-1000x563.jpg (79.04 KB, 83 downloads)
IMG_20190925_162401-1000x563.jpg (72.74 KB, 85 downloads)

Ahh, if only victa had kept producing the thumblatch catcher series, they would be in better shape today!