Reading's hopes of qualifying for the Uefa Cup were dented after a shock defeat by relegated Watford.
Shittu put Watford ahead with a goal out of nowhere
Reading dominated the first half but Dave Kitson's header hit the bar and Leroy Lita was denied a penalty when he was brought down by Cedric Avinel.
Watford made the Royals pay when Dan Shittu slid in Lee Williamson's free-kick on 60 minutes
A superb Ben Foster kept out a Seol Ki-Hyeon effort before Marlon King headed in Tommy's Smith cross.
With Championship football looming, Watford had little to play for against last season's promotion partners.
But to their credit they matched Reading for determination and ensured the Royals stayed seventh in the Premiership - the final qualifying spot for the Uefa Cup.
Reading came out strongly and were soon running the game, with returning duo Steve Sidwell and James Harper influential in midfield.
Chance after chance fell to Lita but he headed Ki-Hyeon's cross wide and then saw Foster brilliantly pluck the ball off his toes in the box.
It was no surprise that the striker reacted angrily when he appeared to be brought down in the box by Watford's debutant Avinel.
The Frenchman had backed into Lita and seemed to hook his legs around the Royals player but referee Dermot Gallagher waved away appeals.
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With Watford failing to make any impression, Reading defender Greg Halford embarked on a storming run out of his own half, dashing past two players and into the area, only to see Foster again quicker to the ball.
Kitson came close to making amends after 32 minutes but his header clattered the bar and the inspired Foster came off his line to deny Lita again just before half-time.
Reading were relentless after the break - but so was Foster, who will return from his loan spell at Vicarage Road to Manchester United this summer.
Lita swivelled in the box and whipped in a low, right-footed shot, only for the keeper to palm it away with his left hand.
No-one could have predicted Watford would take the lead - but they did, when Shittu timed his move to perfection to steal a goal on 60 minutes.
The defender rolled in Lee Williamson's free-kick from the right to put Watford ahead, despite vociferous complaints of offside from Reading.
Reading were momentarily halted in their tracks but Ki-Hyeon came within a whisker of equalising as the home side pressed forward again.
The South Korean midfielder went one-on-one with Foster but the keeper coolly sunk to his knees and punched clear Ki-Hyeon's left-footed shot.
Kitson then put another decent effort just wide but Watford had another surprise in store as King continued his comeback from a knee injury with his first goal since October.
Marcus Hahnemann deflected Smith's cross into King's path and he headed home from six yards to earn Watford a second away win of the season.
Reading boss Steve Coppell:
"Foster was man of the match for them but I don't think loans should be allowed.
"I have serious issues that big clubs can stockpile players and farm them out for top-level football. It's too much of an advantage for them.
"We are disappointed and the Uefa Cup will be difficult for us now."
Watford boss Adrian Boothroyd:
"It would be easy to give up but full credit to the players, they were terrific.
"They showed integrity and character and the win speaks volumes for them not only as footballers but as men.
"We have lessons to learn but we're looking forward to next season. Our fans said it all when they sing, "we're going down but we don't give up".
Reading: Hahnemann, Halford, Duberry, Ingimarsson, Shorey, Ki-Hyeon, Sidwell, Harper (Gunnarsson 79), Hunt (Oster 76), Lita, Kitson (Doyle 81).
Subs Not Used: Federici, Bikey.
Watford: Foster, Doyley, Shittu, Avinel (Mariappa 46), Powell, Williamson, Bangura, Rinaldi (Mahon 10), Smith, King, Henderson (Hoskins 82).
Subs Not Used: Lee, Priskin.
Booked: Avinel, Bangura.
Goals: Shittu 60, King 85.
Ref: D Gallagher (Oxfordshire).