Five (5) runs were needed by Somerset – who was chasing 113 for victory – off the last over which was bowled by Crandon.
With his first ball Crandon bowled top scorer Nick Compton for 31 then Travis Dowlin ran out Gemaal Hussain for a duck to leave the Sabres on 108 for 8 and needing 5 runs from 4 balls.
A single was taken, followed by a double to push Somerset to 111 for 8 and two runs away from victory with two balls remaining.
Steve Kirby then hit a full toss to Dowlin to leave the score 111 for 9 and the Sabres needing two runs from the last ball to win.
Wicket keeping Derwin Christian then affected a last ball run out to leave the Guyanese uncontrollably ecstatic.
Star of the Match Sarwan had top scores for them with 59 as only he and Royston Crandon (10) were able to get into double figures. Guyana got a very meager 112 for 8 from their allotment of overs but with chasing totals proving difficult under lights at the Sir Vivian Richards Cricket Grounds, Guyana hung in until the end.
Opposing Captain Alfonso Thomas grabbed 3 for 23 as the Guyanese innings never took off.
For Somerset, Arun Suppiah made 26 as he and Compton put on 43 for the fourth wicket but once Compton was out at the start of the last over the Somerset innings went into a tailspin.
Guyana 112 for 8 from 20 overs and Somerset 111 for 9.
Meanwhile, Combined Campuses and Colleges sprung a major surprise on powerhouse Jamaica with a comprehensive seven wicket win in their Group A clash in the Caribbean Twenty20.
Chasing Jamaica’s competitive 138 for 4 from 20 overs, CCC timed their run chase to perfection, rocketing to 139 for 3 from 19 overs.
William Perkins struck an audacious 38 from 27 balls while Miles Bascombe – playing on his 25th birthday – cracked 33 from 23 with four boundaries and a six.
Kyle Hope sealed the deal with a measured 32 from 37, ending the proceedings with a stunning extra cover six.
Marlon Samuels, the adjudged Star of the Match lashed a ferocious 80 from 54 balls with five sixes and another five fours as he creamed the CCC attack to all parts of the field and beyond it.
The right hander stroked and pummeled the ball with an equal amount of power and grace in his swashbuckling innings. Wavell Hinds made 21 and Dave Bernard got 20.
Romel Currency had picked up 2 for 27 from 3 overs while Krishmar Santokie took 2 for 16 to top the Jamaica bowling chart.
The upset win by CCC has thrown Group A wide open with four teams – Jamaica, Guyana, Windward Islands and CCC all registering wins. Only Somerset is winless in the group but the English side has only played one game while all the others have played two, losing one and winning one.