Watch These 9 Classic 'Doctor Who' Adventures on Britbox

The most recent seasons of sci-fi sensation Doctor Who are available to stream on HBO Max, and future episodes will come to Disney Plus, but if you want to check out the classic series online they're available on Britbox. If you were intrigued by seeing previous Doctor Who stars in recent episodes of the show -- or if you just want to catch some brilliant TV -- here's our pick of the essential adventures to get you started.

The first ever episode, entitled An Unearthly Child, was broadcast Nov. 23, 1963, and saw a pair of curious teachers investigate a mysterious pupil and her crotchety grandfather -- a man known only as "the Doctor."

The Doctor, played by William Hartnell, turns out to be an alien time traveler. He whisks the teachers away on an adventure in time and space. The magic of the show is evident from the very first notes of the terrifying theme music, making this an obvious starting point.

Now obviously this vintage adventure is from a very different time. The TV of yesterday looks quite quaint to our eyes, but right from the start it's compellingly character-driven with big, intriguing sci-fi ideas in stories packed with mystery, charm and often a genuinely sinister edge.

New Who's season 10 opener, The Pilot, with Peter Capaldi, called back to An Unearthly Child -- see if you can spot Susan in the recent episode.

From the very beginning to the other end of the series. In 1987, seventh Doctor Sylvester McCoy celebrated the 25th anniversary of the show with this rip-roaring adventure.

Remembrance is Who firing on all cylinders: an all-action plot with explosive special effects, new companion Ace creating the template for today's no-nonsense sidekicks, and a subtle call-back to the show's storied history.

Sadly, the show was not to last much longer, but McCoy's era shouldn't be blamed. Episodes like Remembrance, The Curse of Fenric and Battlefield had ambition and excitement in spades.

The new show has seen recent Doctors face villainous cyborgs the Cybermen, but Peter Capaldi took on Cybermen different from those we've seen in the revived show so far.

Capaldi's 12th Doctor faced the return of the very first version of the Cybermen, fabric-masked cybernetic horrors introduced in The Tenth Planet in 1966.

The story is a notable example of early Who for a couple of other reasons. Like several of the early serials, the final episode was lost back in the days when repeats didn't exist and broadcasters simply wiped their old shows.

But it has since been re-created in animated form, which has restored several of the show's missing episodes including the story that followed this one, The Power of the Daleks (pictured). But The Tenth Planet was also notable for one other huge reason.

The Tenth Planet was the final adventure starring an ailing William Hartnell. But instead of ending the show, the creators hit on the novel concept of using our hero's Time Lord physiology to explain a transformation into a new body, a process now known as regeneration. The second Doctor was played by Patrick Troughton.

Now we're talking. Considered by many fans to be the finest Who adventure ever, Genesis sees fourth Doctor Tom Baker arrive at the inception of his greatest enemy to face a mortal moral choice. The philosophical depth of the story perfectly shows why the Doctor is such a compelling character, using intelligence and compassion to defend against evil.

Genesis also introduced the character Davros, adding an extra dimension to the Dalek mythos in terrifying style.

Although he's best known for wandering in time and space, the Doctor has been known to settle in one place -- albeit very reluctantly, when he was banished to Earth for third Doctor Jon Pertwee's swashbuckling tenure. The folk-horror-influenced Daemons is one of the best stories of this excellent era.

Luckily for us, even when the Doctor was stranded, adventure was never far away. It seemed like every week evil lurked in a quaint English village, where the Doctor and his alien-fighting military chums UNIT must save the day. Meanwhile, as in the current show, the Master was never far away...

In The Caves of Androzani, Peter Davison's mild-mannered fifth Doctor and companion Peri land in the middle of an alien political battle that turns into a Shakespearian tragedy of betrayal and revenge.

It's gloriously tense stuff, from which no one emerges unscathed -- including the Doctor.

Longest-serving Doctor Tom Baker takes on a terrifying alien menace in fog-shrouded Victorian London in this much-loved serial. In many ways it encapsulates Who: the Tardis arrives in a historical setting, rendered with the peerless period expertise of the BBC; it includes both sinister villains and engaging secondary characters worthy of their own show; and classic story tropes -- in this case from Sherlock Holmes, Fu Manchu and The Phantom of the Opera -- given an exhilarating sci-fi twist.

And of course, the most classic Who element of all: gloriously terrible special effects.

New Who also brought back classic aliens the Ice Warriors. In their earliest stories the Ice Warriors were depicted as menacing monsters, but the 1972 serial The Curse of Peladon subverts and transcends such simplistic storytelling.

Curse is a great example of how sympathetic Doctor Who often is towards those who appear different or threatening, and why the Doctor shows compassion no matter who plays the role.

It's only fair to mention each of the original seven Doctors, so we've thrown in this 1985 political satire to represent Colin Baker's sixth Doctor. But between you and me, it's OK to turn this off and watch a Tom Baker one instead.

With 26 seasons of classic Doctor Who available on Britbox, that should keep you busy even as the new show celebrates its 60th anniversary in 2023 with new specials starring David Tennant.