The two left-handers shared a second-wicket stand of 175 and although opener Joyce was out shortly after reaching his 11th one-day hundred 21-year-old Machan, who was playing only his third List A game for Sussex, pushed on to score an undefeated 126.
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The Government scheme would benefit those aged under 40 but will only run for five years.
Becoming windy with cloud and showers this afternoon. Heavy rain on the way later
Becoming windy with heavy rain later