Titanic, ITV1

Imagine my surprise when we weren't much more than halfway through this first episode, and the flipping thing hit the iceberg. But of course writer Julian Fellowes was way ahead of me, and his four-part series about RMS Unsinkable is evidently going to circle around the vessel's fate from various viewpoints in assorted time frames.

Judging by the trailer at the end, next week's is going to home in on such prickly issues as whether the Titanic was going too fast or keeping an adequate look-out for floating hazards, and whether or not she was as safe as the designers claimed. In this opener, there was a scene in which Bruce Ismay (James Wilby), supremo of the White Star Line which operated the Titanic, firmly quashed the idea of installing a possible 32 lifeboats, opting instead for a scant though still legal 16. "I will not have the promenade deck ruined or the ladies terrified out of their wits," he boomed. We were drowning in dramatic irony before they'd even started the engines.

But most of part one was given over to a rather pernickety examination of the class structure of the Titanic's seaborne society. Deep in the bowels of the vessel, stokers shovelled coal into roaring furnaces to fuel the engines, the flames throwing diabolical shadows across sweaty faces. As the posh people ate their dinner in lavishly-appointed dining rooms, they might find themselves being served by an adventurous Italian en route to seeking his transatlantic fortune. Maids and valets of English noblemen or American billionaires jostled abrasively for position on the lower decks.

There were rather too many characters who remained unrecognisable or interchangeable, and though Fellowes has served up a sizeable cohort of American travellers (great for potential US sales, but historically accurate too), he hasn't avoided the curse of British actors speaking insipid pidgin Yank. It really isn't that difficult, surely? There were also a few neon-lit infomercials to fill in a bit of social background, as when the young heir from Philadelphia, Harry Widener (Noah Reid), observed, as he twirled Lady Georgiana (Perdita Weeks) round the dancefloor (pictured above), that he saw no likelihood of the British giving up their class system because it was "woven into their character."

Fellowes has previously fallen foul of accusations that he's a true-blue toff with an unshakeable allegiance to his caste, but his portrayal of the aristocratic Brits here was anything but complimentary. We saw a lot of Hugh, Earl of Manton (Linus Roache), who made it plain to Ismay that he'd better find a suitable berth on board for his daughter Georgiana, or else. Moments earlier, we'd seen the Earl springing Georgiana from a jail full of thieves and prostitutes after she'd assaulted a policeman during a suffragette rally, and he coldly put an uppity copper in his place in the process.

His wife, the Countess Louisa (Geraldine Somerville), then turned out to be an Olympic-class snob, shivering with disgust at virtually everyone she met on board the giant liner. Celia Imrie (pictured left), playing dog-loving nouveau riche Grace Rushton apparently in the style of Gracie Fields, was struck dumb by an acid put-down from the Countess: "We are a political family. You, I think, have always been in trade." Madame Aubart (Joséphine de la Baume), mistress of American businessman Benjamin Guggenheim, so offended Louisa's sense of decorum that she was made to leave the tea room before Her Ladyship would enter it.

Still, payback time wasn't long in coming. As the panicky passengers scrambled for the lifeboats, the Mantons were furiously denounced by defiant Irishwoman Muriel Batley (Maria Doyle Kennedy, a familiar face from the Fellowes repertory company as the first wife of Bates the valet in Downton Abbey). The Earl's infidelities were loudly announced, though it transpired that his wife had known about them all along. As the credits rolled, she was left impaled on the dilemma of whether to join the women and children in the lifeboats, or stand by her man on the tilting deck.