Britain and the Tunguska area are so far apart - with so much surface curvature in between - that an explosion even several miles above ground could not be seen by line-of-sight. They must have seen the item while it was still in the stratosphere, well before ground contact - so the black hole theory still works.
“To the Editor of the Times.”
“Sir,--Struck with the unusual brightness of the heavens, the band of golfers staying here strolled towards the links at 11 o’clock last evening in order that they might obtain an uninterrupted view of the phenomenon. Looking northwards across the sea they found that the sky had the appearance of a dying sunset of exquisite beauty. This not only lasted but actually grew both in extent and intensity till 2:30 this morning, when driving clouds from the East obliterated the gorgeous colouring. I myself was aroused from sleep at 1:15, and so strong was the light at this hour that I could read a book by it in my chamber quite comfortably.
At 1:45 the whole sky, N. and N.-E., was a delicate salmon pink, and the birds began their matutinal song. No doubt others will have noticed this phenomenon, but as Brancaster holds an almost unique position in facing north to the sea, we who are staying here had the best possible view of it.
Yours faithfully,
Holcombe Ingleby.
Dormy House Club, Brancaster, July 1” (1908)