[adal]

A lot of year’s ago my dad when planting Brussels sprouts would use the back of his Heel (shoe) at the base of the plant then put a cane in for support.  Do Brussels sprouts need a firm hold?  And support’s. The allotments were not far from the sea. Would you still have to do this as I live inland now?

[Nikkithefoot]

All brassicas much prefer their roots in solid ground.Sprouts probably more so other wise they have a tendency not to form proper sprouts they blow instead. The cane could be useful if you are on a windy site to help support them as they grow taller and stop them rocking in the ground and working themselves loose

[penance]

Yes they like very firm ground, as do all brassicas.
And staking is worthwhile as they grow fairly tall.