It may not have come to your attention (technically speaking it's not even true) but the BBC maintains an informal company of talented actors who can turn on a sixpence, moving from shouting unwieldy exposition in mainstream drama, into warty, batty character parts in Dickens. Whether young or old, they are regarded as national treasures, and are probably in Little Dorrit. As a service to you, the reader, here's a brief list of the company's members.
(1) Alun Armstrong has enjoyed thirty years of discreet ubiquity. His engagingly jolie-laide face exudes both compassion and integrity and is consequently spotted in every Dickens serial ever made (Little Dorritt? Of course.) He's neurotic Brian Lane in the hugely popular New Tricks, but his grade one listed actor status was confirmed by a subtle and moving performance in Filth.
(2) Janine Duvitski is royalty, having starred in Abigail's Party and The Blue Remembered Hills. Like Alun Armstrong, she uses her appealing, unconventional looks to her advantage. Passes the Dorrit test, and served time at sitcom boot camp on One Foot In The Grave.
(3) Amanda Redman is a TV fixture, gradually climbing the rickety rope ladder from glamorous blonde to character actress via Hope St. Earned her dressing room key by dint of New Tricks, where she plays strong-but-flawed Supt Sandra Pullman. Has some Dorritt action.
(4) Just as British films must, by law, feature Ewan McGregor, the same is true of Martin Shaw and BBC drama, where he's usually seen smouldering as a game, world-weary yet sparky old hand. Too busy for Dorrit, he's been in Cranford, Rhodes, Judge John Deed, and George Gently. He even twinkles in the bizarre Apparitions.
(5) The new king of BBC drama is David Tennant. Demonstrated early versatility in the fantastic Taking Over The Asylum, and as a transvestite in Rab C Nesbitt. Costume drama? Of course (He Knew He was Right). Already a fixture in the rep, appearing in Blackpool and Casanova, there's a shiny Bafta award with his name on it for his beautiful performance in Einstein and Eddington. Job for life.
(6) Freema Agyeman is too young to nail her colours to the BBC's mast. What if she can do a Scottish accent and wants to appear in Taggart? (Well, she's got the range.) Confusingly, was in Dr Who twice as two separate characters (bless that hyper-phasic Equity continuum.) Agyeman also reads bedtime stories for CBeebies, and is in Survivors. For Little Dorritt she plays the incandescently infuriated foundling girl Tattycoram.
Obviously this list is far from complete. Do you have anyone else to add?