Goals late in the first half from Dave Cowley and James Baker did the damage. Jamie Guy pulled one back with a 78th-minute penalty and, after Sudbury’s Rhys Darg was sent off, James Robinson missed a late chance to equalise.
Grays, who have three games in hand, closed the gap to ten points as Jack West scored two minutes before the break to give them a 1-0 win at Brentwood.
Heybridge moved above Thamesmead into fourth place after snatching a 2-2 home draw with Needham Market. Jemel Fox gave the visitors a first-half lead and it looked all over when Tom Dew made it 2-0 in the 85th minute. But recent signing Grant Cooper pulled one back and Solomon Ofori levelled it in added time.
Witham, in sixth place, edged a little closer to the play-off places after Rob Whitnell netted the only goal of their home game with Wroxham with only two minutes left. But Witham who had earlier missed a penalty, are still nine points behind Thamesmead.
Soham maintained their distant play-off hopes by easing to a 3-0 home win over Redbridge. Luke Stanley scored twice in the first half and Robbie Mason netted his 19th league goal soon after the interval.
The losers remained a point ahead of bottom club Ilford, who were beaten by an 18th-minute goal from Austin Gacheru at Chatham.
Tilbury were 2-0 winners at Potters Bar thanks to a Sam Cutler penalty just after half-time and a Shamir Mullings header two minutes from the end.
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