1930: 82nd BOAT RACE - Cambridge by 2 lengths. Oxford 40, Cambridge 41. See Boat Race 1930s

Oxford Crew, 1930

1930: HEAD OF THE RIVER - Brasenose

1931: 83rd BOAT RACE - Cambridge by 2½ lengths. Oxford 40, Cambridge 42. See Boat Race 1930s
1931: HEAD OF THE RIVER - Brasenose

1932: 84th BOAT RACE - Cambridge by 5 lengths. Oxford 40, Cambridge 43. See Boat Race 1930s
1932: HEAD OF THE RIVER - Magdalen

Oxford Crew man practicing in front of a mirror so as to acquire correct form
Popular Mechanics

1933: 85th BOAT RACE - Cambridge by 2¼ lengths. Oxford 40, Cambridge 44. See Boat Race 1930s
1933: HEAD OF THE RIVER - Oriel

1934: 86th BOAT RACE - Cambridge by 4¼ lengths. Oxford 40, Cambridge 45. See Boat Race 1930s
1934: HEAD OF THE RIVER - Oriel

1935: 87th BOAT RACE - Cambridge by 4½ lengths. Oxford 40, Cambridge 46. See Boat Race 1930s
1935: HEAD OF THE RIVER - Oriel
From the 1935 Eights programme -

Map from the 1935 Eights programme

1936: 88th BOAT RACE - Cambridge by 5 lengths. Oxford 40, Cambridge 47. See Boat Race 1930s
Cambridge's 13th succesive win.
1936: HEAD OF THE RIVER - Oriel

1937: 89th BOAT RACE - Oxford by 3 lengths. Oxford 41, Cambridge 47. See Boat Race 1930s
A slight foul to which Merrifield [Oxford cox], though in the right, gave way, and [Hammersmith] bridge was shot dead level.
And here is a photo just after the foul. Extend the wakes back and I think you can see they have just suddenly gone apart.

1937, photo from Hammersmith Bridge, Oxford on left, just after slight foul. Roughish water!

Oxford win in 1937

John William Pitt: "The River Thames - a descriptive poem"

The famous Boat-Race winning post not far below appears,
And here, in nineteen thirty seven, after many years
Of patient striving, Oxford's crew, by two full boat-lengths, beat
The Cambridge one, a well-earned change from fourteen years' defeat.

1937: HEAD OF THE RIVER - New College

Torpids, 1937

1938: 90th BOAT RACE - Oxford by 2 lengths. Oxford 42, Cambridge 47. See Boat Race 1930s
George Drinkwater in his book 'The Boat Race' ended with the 1938 race -

And so we leave the race, which it may be hoped will never again be interrupted as it was from 1914 - 1918

It was that moment before World War II when Chamberlain proclaimed "Peace in our time". It was not to be. There would be only one more boat race before the world fell apart, and no doubt George Drinkwater took notes ready to write it up for his next edition. But there was no next edition.
George Drinkwater, Oxford Blue, Bow in 1902, 7 in 1903, died in an air raid.
1938: HEAD OF THE RIVER - Trinity
Gertrude and Muirhead Bone published "Came to Oxford" in 1952 - but I think the descriptions and illustrations are 1938 -

Eights Week, "Came to Oxford", Muirhead Bone

But these [the Cherwell et al] are the lilies and languors of the river.
The Shining Mile is stern endeavour.
(To forestall any remonstrance from earnest people, I chronicle the fact that the length actually rowed by the College Eights is one mile and two furlongs.)

'Rugby? Oh you mean to play Rugby? Well, of course, I've nothing against Rugby. It's a nice little game.
But remember! A College stands by its boats!'
You are impressed by that visit of the great Captain of Boats. You join the band of consecrated oarsmen sitting apart at table. You eat next-to-raw beef steaks. No smokes! No drinks!
'The College stands by its boats!'
You frequent the river. I have a fancy for it on a winter morning of frost shining in sunlight. From one of those ancient narrows for defence called a gut you look on a silver river at pause. The towing-path is empty. The free ferry crosses a gleam with the gravity of Time on the dial. You look back and forth at that bend in the path and see a clear and empty river shining and waiting, the shining mile of hope lying under the willows with their threatening fists. And all the Term, for you the river bears the weight (rolling smooth again after washing high up to the roots of the willows) of the splashing and striving of boats - your boat!
Your muscles ache! You patiently endure a great deal of flyting from an irascible coach on a bicycle. You steady your stroke; your leg-work improves; a grunt of approbation heartens you for a week. Term goes by and you can do nothing else. You begin to wish you hadn't - and then it comes! Mastery over those difficult paces, easy muscle, conquered breathing! You walk like a person apart and precious. Nothing less than the shining mile for you!

Eights Week: From Christ Church Boat House, "Came to Oxford", Muirhead Bone

It's nervous work when it comes; when the boat swings out from the barge and you settle your legs and strike water under the eyes of the elegancies in appropriate costume, and the other men of the College.
The elegancies you don't mind so much. After all they are probably more afraid of you than you are of them. But the appraising eyes of the other men and other crews - these are the formidable tests.
'The College stands by its boats!'
Once out on the shining mile you are spared the laments of the longshoremen that the Eights 'isn't what it was!'
'Why! I can remember the time when there was bands playing and they trimmed the barges up with flowers. Hundreds, thousands, there was! It's nothing like it was in my young days.'
You don't hear how the weather is always bad at the Eights - 'of course today's an exception!'
You hear nothing of these disclaimers as you measure your shining mile - three heart beats to two strokes, a difficult rhythm. They are beautiful things these swallow-tapered boats and not all longshoremen are captious. I was peering through a certain railing which gives a long sight of the boats when Oriel swung past - a boat and crew who had found themselves and were everything that a College longs for in the way of rowing, when I heard a voice chanting beside me, and all for its own pleasure too, not in the least for my information,
'A lovely crew! That's lovely rowing! A lovely crew that is!'
If the gentleman had been Welsh (perhaps he was) I should have said that the delight of his subject had brought him into the Hwyl, for he sang on in a fine afflatus till they were past.
For a sight of the finish and beauty of water-craft wait for the parade of the golden boats at the end of the Eights, and after it is all over except a few belated pistol-shots to carry you on to the next Eights week, slip under the alders and beech beside the Cherwell and see the apotheosis of all that is charming in English rivers. Perhaps just because I was not expecting it, the sight seemed to me especially delightful. The sunlight slanted over the buttercup-meadows of Christ Church and the whitethorn shook all its fragrance into the light. Scarlet thorns, heavy to the ground with blossom, made a quiet brilliance on the green bank of the river. Foundations of beryl and jasper lay in the water by the tunnel of birch and alder when the returning punts broke through. By ones and twos at first and then in a medley they came, drawn, it seemed, by teams of coloured balloons and urged on by the gay voices of girls.
They drew homeward and away and as I watched them I thought that the return of the punts from the last of the Eights on that superb evening of May, one of the prettiest sights I had ever seen in England.

Eights Week, the return of the Punts: "Came to Oxford", Muirhead Bone, 1938

1939: 91st BOAT RACE - Cambridge by 4 lengths. Oxford 42, Cambridge 48. See Boat Race 1930s
1939: HEAD OF THE RIVER - Trinity

After ninety one boat races the overall tally was Oxford 42, Cambridge 48 (and one dead heat)
From 1924 to 1936 Cambridge won all 13 Boat Races, the longest unbroken run to date.
In 1930 Cambridge went into the lead for the first time since 1862.
Leadership in Overall Tally of Boat Race Wins:

1829	1939