The damage was done on Tyneside in the first leg last Sunday after the Monarchs returned north of the border with a 49-41 victory.
A depleted Newcastle side arrived at Armadale with just five riders for the return leg, the Diamonds operating rider replacement for No.1 Bradley WIlson-Dean and ex-Monarch Willie Lawson coming in at No.5 for Paul Starke who was suffering with a bout of food poisoning. Read into that what you will.
The hosts had all but sealed their place in the last eight after four races, a 16-8 lead with Sam Masters, Kye Thomson and the impressive James Sarjeant all with race wins under their belts.
Former league winner with the Monarchs Matty Wethers was the first Diamond to see the chequered flag in heat five but his team-mate James Wright couldn't find a way past Thomson or Paco Castagna for a heat advantage they so desperately craved.
Sarjeant outfoxed Wethers to take a battling win - his third of the night - to preserve the Monarchs' eight-point lead at the midway point. Crucially, the Capital outfit were 16 points clear on aggregate and home and dry barring a miracle.
To their credit, Wethers and Max Clegg continued to fight for the cause but a 4-2 in heat 11 from Pickering and Jacob Hook increased Monarchs' lead to ten and, with that, a quarter-final showdown with their arch rivals.
A third 5-1 of the evening saw the Monarchs pull 18 points clear 48-30 with just two heats remaining.
Young Australian Hook rode a fine line to finish with a paid win in the penultimate race before top duo Masters and Pickering compounded the Diamonds misery with another 5-1 to secure a comprehensive 58-32 win – 107-73 success on aggregate.
Sarjeant, Masters and Pickering all finished with paid maximums and will take a lot of confidence ahead of a double header against Glasgow in the Championship next weekend.
Monarchs: Masters 14, Pickering 13, Sarjeant 11, Thomson 8, Castagna 7, Hook 4, Fredriksen 1.
Diamonds: Wethers 10, Clegg 8, Complin 6, Wright 4, Congreve 2, Lawson 2.