Leus du Plooy piles the misery on Gloucestershire

Teenage tailender Sebastian Morgan narrowly missed out on a maiden career hundred as Middlesex racked up the joint fifth-highest total in their history against Gloucestershire at Lord's.

Morgan, who turned 18 last month and is making his third first-class appearance, was out for 97 after sharing a partnership of 179 with his captain Leus du Plooy - a county record for the eighth wicket against Gloucestershire - to help Middlesex amass 634 for 9 declared.

Du Plooy also posted his best first-class score, an unbeaten 263, to put the visitors firmly under pressure in their final Rothesay County Championship game of the season, despite Ajeet Singh Dale's return of 5 for 108.

Gloucestershire openers Ben Charlesworth (63) and Joe Phillips (36) responded with a century stand before three wickets fell for eight runs, two of them to spinner Zafar Gohar against his former team.

Singh Dale, stuck on four wickets since the previous afternoon in his farewell game for Gloucestershire, lost no more time in completing a five-for, with Joe Cracknell taken low at slip for 64 in the seamer's first over of the morning.

He might have claimed a sixth victim soon afterwards when former team-mate Gohar swished outside off stump, but this time slip fielder Ollie Price could not cling onto the chance.

It was spinner Graeme van Buuren who eventually removed Gohar, dragging on from a long way outside off stump and his dismissal seemed to dispel any Middlesex thoughts of making a dart for a fifth batting bonus point.

Instead, Du Plooy sidled towards 200 while Morgan kept the scoreboard ticking along with an early brace of sweetly-struck fours off Marchant de Lange and went on to dominate the partnership.

Du Plooy eventually emerged from his shell, charging down the track to drive Price over the top for four to seal his double ton from 294 balls, while Morgan's half-century arrived soon afterwards courtesy of a leg-side clip to the fence off Singh Dale.

Despite a spell of playing and missing to Matt Taylor just after lunch - and a return chance on 72 that De Lange was unable to grab - the teenager continued to flourish, expanding his repertoire to include a slog sweep and reverse sweep.

Both were productive against Gloucestershire's spinners, with a six off Jack Taylor ushering the total past the 600 mark shortly after identical tactics by Du Plooy had lifted his personal score beyond 250.

But Morgan's decision to attempt another reverse sweep against Price proved his undoing as he overbalanced while James Bracey took off the bails and, after a quickfire 19 by Toby Roland-Jones, the declaration soon followed.

That left Phillips and Charlesworth to navigate 10 overs until tea and they did so with little cause for concern, the left-hander looking strong off his pads as well as punching Roland-Jones for two cover boundaries.

Successive fours off Noah Cornwell took Charlesworth along to 50 at just under a run a ball and he continued on the offensive, using his feet and dispatching Gohar over the top twice in an over.

Phillips gained a life when Roland-Jones found the edge, only for Sam Robson - diving across from slip - to shell the chance, but the seamer did achieve a breakthrough in his next over as Charlesworth tried to cut and Cracknell snared a tumbling catch behind the stumps.

Gohar then struck twice in quick succession, pinning Phillips lbw before a looping bat-pad catch accounted for Miles Hammond, but Price and Bracey guided Gloucestershire to the close with another 339 needed to save the follow-on.