What does "unlikely neighbourhood" mean in "A Fisher of Men"?

Question

In "A Fisher of Men" in Dr. Thorndyke's Case-Book by R. Austin Freeman, Thorndyke was talking about a man who went to visit another one who wants to buy his expensive necklace, saying:

"Mr. Montague's destination was Isleworth, in which rather unlikely neighbourhood Mr. Jacob Lowenstein, late of Chicago, and now of Berkeley Square, has a sort of river-side villa with a motor boat-house attached. Lowenstein had secured the option of purchasing the blue diamond necklace, and Montague was taking it down to exhibit it and carry out the deal."

I know the meaning of "unlikely" itself, but I can't see its meaning in this context! Does it mean "remote" or "strange"?

And what is meant by "secured the option"?

Answer 1

Isleworth is described as an "unlikely neighbourhood" because Dr. Thorndyke would not have expected of men of such means to live there. According to Wikipedia, Isleworth during Georgian and Victorian times had attracted many "aristocrats and high achievers" who built "many mansions and large houses". From this perspective, it would not have been strange for someone who wants to buy a £70,000 necklace to have a residence in Isleworth. However, railway expansion in the second half of the 19th century also brought factories to Isleworth, which may have made the town less attractive to the rich by the early twentieth century. (Dr. Thorndyke's Case-Book was published in 1923.)

Mr. Jacob Lowenstein had "secured the option" to buy the necklace, i.e. he had paid a nominal fee to ensure that Mr. Lionel Montague's firm would not sell the necklace to another buyer before he (i.e. Lowenstein) had decided whether he wanted to buy it or not.