Hampshire 296 (Weatherley 98, Northeast 51, Murtagh 4-61) and 161 for 7 (Weatherley 64*) beat Middlesex 252 (Andersson 92, Stevenson 4-70) and 201 (Organ 4-42) by three wickets
Joe Weatherley was Hampshire's hero as he kept his cool with an unbeaten half-century to clinch a tense three-wicket victory against Middlesex in the Bob Willis Trophy.
The opener - who top-scored with 98 in the first innings - stood firm again despite a clatter of wickets on the fourth morning at Radlett, sealing Hampshire's success with a cover-driven boundary off Tom Helm as he finished 64 not out.
Weatherley shared an unbroken eighth-wicket stand of 53 with Keith Barker (28*) to steer the visitors over the line after Tim Murtagh and Thilan Walallawita had raised Middlesex hopes of an unlikely triumph with three wickets each.
The pair reduced their opponents to 108 for 7, with Liam Dawson already out of the game due to a torn Achilles tendon and last-man Ryan Stevenson, who was also injured after colliding with a marquee pole while fielding on the previous day, standing by to bat with a runner if necessary.
Hampshire began play as clear favourites at 60 for 2, needing another 98 for victory, but they were checked by Murtagh's second ball of the day, which Sam Northeast edged onto his pad for Max Holden to scoop up the catch at point.
New batsman Ian Holland was fortunate to survive his first delivery, which found the edge but was spilled by second slip Nathan Sowter and he took advantage with some attacking shots that raised the scoring rate.
Left-arm spinner Walallawita applied the brakes, stemming the flow of runs to a trickle and piling renewed pressure on the Hampshire batsmen - which Murtagh gratefully exploited at the other end.
Sowter made amends for his earlier drop, taking the catch off Murtagh to prise out Holland for 17 and, when Harry Came fell to a tumbling Sam Robson at first slip, the visitors were in trouble at 87 for 5.
While Weatherley dropped anchor, Lewis McManus took up the baton with a cameo of 13, but he was bamboozled playing back to Walallawita, who then had James Fuller caught behind prodding outside off the stump in his next over.
However, Barker - hobbling throughout due to a foot injury - revived Hampshire's hopes by reverse-sweeping Walallawita to the boundary and picking up four more with an on-drive off James Harris.
Weatherley completed his half-century, from 159 balls, during the second over after lunch, driving Sowter through mid-on for four, while Barker weighed in with two more boundaries before his partner applied the finishing touch.
"It was a hard-fought four days and I think we just about deserved it in the end," said Northeast, Hampshire's captain. "Joe Weatherley's played two fantastic innings and he's really showing his potential for the future for Hampshire, which is great. Barks, with his little cameo at the end, was just what was needed to release a little bit of pressure.
"You sort of forget the first three days when it comes down to tight moments like that. We've obviously lost two key members of our side during the game as well and it wasn't easy, but I'm very pleased to get the win."
"We'll look back on periods, namely when they were about 30 for 3 in their first innings and we dropped a couple of chances and could have bowled them out for about 150," said Stevie Eskinazi, Middlesex's captain. "Then when we were over 100 for 2, we had the game by the scruff of the neck and couldn't quite hammer home the advantage.
"The difference in this game is, if one bloke goes on [with the bat], then we're putting the game to bed. I can't fault the lads' effort over the four days. We played some good cricket but we probably didn't deserve to win this game."