In the Mixed Pairs - BC3, the gold medallists from Beijing 2008, the Republic of Korea, suffered defeat in their opening pool match as they lost 5-4 to Canada, before following that result up with a 6-2 win over Great Britain.
The Host Nation are the reigning champions in the Team BC1-2 and overcame a stubborn Argentina side 8-4 in their first game. The two teams were locked at 4-4 at the start of the sixth and final end and it took a brilliant shot from Great Britain's David Smith, across almost the entire width of the court, to shake off their opponents.
'It was about weathering the storm for the first five ends and then we ground them down. We knew we just needed to win the (final) end,' said Smith, who then helped the British quartet to a 5-4 win over Portugal in their second match to progress to the quarter-finals.
In the Pairs - BC4, meanwhile, Beijing 2008 champions Eliseu Dos Santos and Dirceu Pinto of Brazil were in scintillating form as they began their defence of their title with a 10-0 win over Portugal, before beating Hong Kong 7-4 in Pool A.
'The key factor is that we did a pre-season, for example a week-and-a-half in Manchester. That helped us improve. And our trainer has used some innovative strategies,' revealed Dos Santos.
It was the performance of the Thailand quartet of Witsanu Huadpradit, Mongkol Jitsa-Ngiem, Pattaya Tadtong and Watcharaphon Vongsa, however, that really caught the eye.
The world number two-ranked side in the BC1-2 event beat Canada 22-0 in their opening group game to lay down a serious marker in Pool B, before beating China 8-3 in their second match of the day.
In the same competition, world number one team the Republic of Korea were also in fine form on the opening day as they beat Ireland 14-3 and Brazil 10-3.
Japan also recorded two wins from two in Group D as Beijing 2008 bronze medallists Spain lost 6-4 to Hong Kong - the lowest ranked of the 12 teams in the event - before losing to the Japanese.
The favourites going into the Pairs - BC3 were world number ones Greece and, inspired by captain Grigorios Polychronidis, they started out with 5-0 and 3-2 wins over Great Britain and Canada respectively.
Elsewhere in the Pairs - BC4, Czech Republic assured themselves of a semi-final place by beating Portugal 6-1, to follow up their earlier victory against Hong Kong, while Canada sprang a surprise in pool B by beating Great Britain's number two ranked pairing of Stephen McGuire and Peter McGuire 4-1.