In what has been a difficult week for organisers, the races were switched to a duathlon after early morning water tests showed high levels of E-Coli in Odaiba Marine Bay.
It meant the traditional first leg of a 750m swim was replaced with a 2.5km run, with the usual 20km bike and 5km run to follow.
The change of format did not deter the British contingent, with Townsend taking advantage of the absence of imperious Dutch duo Jetze Plat and Geert Schipper to lay down a marker for next year.
The former Royal Marine commando was first to take the tape in the wheelchair division, pulling back the head-start given to Ahmed Andaloussi due to his higher level of disability, to win by over 1min.
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It was a British one-two in the PTS5 category where Steadman took the honours, reversing the result over fellow Brit Claire Cashmore from the Montreal World Series race in June and the national championship in May.
The Paralympic silver medallist from Rio produced a final 5km run of 20:26 to break away and win by 94sec, with reigning Paralympic champion, Grace Norman of the USA, in fifth.
With both Steadman and Cashmore former Paralympic swimmers, being able to take the top spots on the podium despite a revised run-bike-run format, outlined why the women’s PTS5 division is arguably the strongest hope for British medals next year.
The third British winner was Dave Ellis in the visually impaired category who was guided by three-time Olympian Tim Don. Ellis had missed out on Rio when his category was not among the nominated three men’s classes, but proved too fleet of foot, with a 16:39 final 5km to run out a comfortable winner.
Cornwall’s Melissa Reid also picked up silver in the PTVI class behind Jessica Tuomela of Canada, describing it as “one of the hardest races I’ve ever competed in”.
Fran Brown matched Reid’s feat in the PTS2 class where she was runner-up behind Hailey Danz of the USA. The 34-year-old from London is a former climber and has yet to finish off the podium in any paratriathlon she’s started.