THE robots in disguise continue their age-old feud in the eagerly-awaited sequel to one of the biggest box office hits of 2007.

Director Michael Bay (Armageddon, Pearl Harbor) returns to the helm for Transformers: Revenge Of The Fallen to destroy large swathes of planet Earth in a miasma of pyrotechnics and computer-generated imagery, courtesy of the wizards at Industrial Light & Magic and Digital Domain.

The second film pushes the visual effects envelope with more outrageous slam-bang thrills, apocalyptic set-pieces and skirmishes between the noble Autobots and their sworn enemies, the Decepticons.

At times, the screen becomes a blur of entangled, shiny automaton limbs and it's difficult to work out who has the upper hand until the dust settles or, as in the film’s most heart-tugging moment, one of the metal monsters powers down for good.

Steve Jablonsky’s booming orchestral score begins at an ominous growl for a throwaway prologue in 17,000 BC and steadily increases in volume to match the on-screen crash, bang, wallop.

Two years have passed since high school student Sam Witwicky (LaBeouf) and his Autobot friends defeated power-hungry Megatron (voiced by Weaving).

In the intervening period, humankind has forged an alliance with Autobot leader Optimus Prime (Cullen) to create a top-secret military division known as NEST, which hunts down the last remaining Decepticons.

Field commanders Major Lennox (Duhamel) and USAF Master Sergeant Epps (Gibson) lead these covert missions, flanked by Ironhide, Jazz, Ratchet and some new additions to the Autobot fold.

Meanwhile, Sam prepares for his first year at college by bidding farewell to his parents (Dunn, White), beautiful girlfriend Mikaela (Fox) and robot protector Bumblebee.

In the middle of class, Sam experiences powerful visions of hieroglyphs, and as these hallucinations become more intense the young man senses that Autobot leader Optimus Prime has been keeping secrets from him.

Sure enough, the Decepticons are preparing to return to Earth in even greater numbers to fulfil an ancient prophecy.

Transformers: Revenge Of The Fallen overstays its welcome by at least 30 minutes with a middle section that sags badly, as Sam and co join forces with college room-mate Leo (Rodriguez) and former agent Simmons (Turturro) to unravel the mystery of the symbols.

The introduction of a Decepticon called The Fallen echoes Star Wars, while chaotic scenes of appliances in the Witwicky family home coming to life are an obvious nod to Gremlins.

Bay orchestrates action sequences with customary lack of subtlety, employing slow motion ad nauseum as American derring-do once again rescues humanity. Fox reapplies her lip-gloss unseen during each bravura stunt sequence. While entire cities fall, her pout remains lustrous.

If Major Lennox would only melt Megatron and his minions using sunlight reflected off those lips, the Decepticons would be banished far sooner and we wouldn't spend the last half-hour glancing at our watches.