Vaughan took 4 for 31 from his nine overs, figures which would have been even better had his last two deliveries not been hit for sixes by John Stephenson. McGrath had earlier helped manoeuvre his side from a precarious 43 for 5 to set the hosts a reasonable target.
Yorkshire's rivals and last season's champions, Lancashire Lightning, moved into second spot thanks to another stunning display of hitting from the England all-rounder Andrew Flintoff. Flintoff slammed 45 from just 35 balls to help secure an easy six-wicket win over Warwickshire Bears at Edgbaston.
The seam bowler Peter Martin had earlier made the most of the unreliable surface as he took 5 for 28, including the last four wickets, and Sri Lanka off-spinner Muttiah Muralitharan again proved almost unplayable as he conceded just 13 runs from nine overs as the Bears struggled to 127 all out.
Min Patel proved to be the key figure as Kent Spitfires pulled off a 20-run victory over Essex Eagles at Chelmsford. Replying to Kent's 245 all out, Essex looked to be well in command as openers Nasser Hussain and Darren Robinson carried the score into three figures in the 21st over. But then their challenge went sadly awry as left-arm spinner Patel made a dramatic impact - including the wicket of dangerman Stuart Law in his 3 for 44. Hussain struck 65 but Kent were always in control from the moment Law departed for a duck.
The Kent innings was built around Andrew Symonds, who drove with immense power on his way to 85 from 79 deliveries, an effort containing two sixes and six fours.
Gloucestershire Gladiators slipped to fourth after a 38-run defeat by Leicestershire at Bristol. It was the Foxes' second victory in succession after a poor start in the competition.
They posted 214 all out off exactly 45 overs after their captain Ben Smith had won the toss in glorious sunshine. Ian Harvey claimed 5 for 41, mopping up the Leicestershire tail. But Gloucestershire's batsmen never looked up to their task as James Ormond and Darren Maddy claimed three wickets apiece as the home side crumbled to 176 all out in 41.1 overs.
In Division Two Michael Di Venuto fired an unbeaten 72 as leaders Sussex maintained their 100 per cent record by overpowering Durham by seven wickets.
Alec Stewart's batting woes continued. He scored just two as Surrey Lions slipped to a narrow five-run defeat against Northamptonshire Steelbacks at Wantage Road.Reuse content