Thames ward has a new Labour councillor.
Fatuma Nalule's triumph in the by-election keeps Barking and Dagenham as an all-Labour local authority.
Ms Nalule secured 1,545 votes following the election on May 6.
Of her five opponents, the closest challenger was Conservative candidate Andrew Boff, who received 939 votes.
The four remaining candidates - Independent Sabbir Zamee, Trade Unionist and Socialist Coalition's Pete Mason, Lucy Ewube Baiye-Gaman, from the Christian Peoples Alliance Party, and Liberal Democrat Afzal Sayad Munna secured 574, 345, 158 and 81 votes respectively.
During her victory speech, Ms Nalule said: "I want to thank the residents of Thames ward who have voted; they have given their time to cast their vote to make the right decision."
She also thanked her team for their help during the campaign.
Whilst awaiting her fate at Saturday's count, Ms Nalule spoke of feeling "positive and confident".
Vowing to give residents "even more of a voice" if elected, her campaign was driven by the pledge to "build bridges" between community and council.
A controversial moment came when Conservative candidate Mr Boff bucked tradition to take to the stage following Ms Nalule's victory speech.
As part of the impromptu address, he thanked his campaign team and agent, with an accompanying reference to being "united by a passion for the people and unspellable surnames".
This latter remark caused a stir among those watching on, including council leader Darren Rodwell, who accused Mr Boff of using "inappropriate language" aimed at the borough's diversity.
Mr Boff denied this accusation, stating that the comment referred to his campaign team - Tilly Wijesuriya, Eunice Acheampomaa and agent Martynas Cekavicius - who all have "unpronounceable, unspellable surnames".
He described the allegation as "woke rubbish".
The Conservative candidate had earlier taken issue with the vote count; this was resolved without a re-count.
Before a winner was declared, Cllr Rodwell talked up the prospects of the borough's newest councillor.
Describing Ms Nalule as a "wonderful candidate", he said: "We're a Labour borough through and through, and I think people know that - despite our difficulties - we're all in this together."
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