This is a book by another rather forgotten Rabbi, Jacob Leib Davidson, a long -time resident of South Tottenham. Rabbi Davidson was born on 23rd July 1875, and died in London in 1960. According to Rabbi Joseph Unterman (who was Rabbi of the South Tottenham Synagogue), writing his obituary in the Jewish Chronicle, he was a Talmudic scholar of wide renown. Rabbi Jacobson was formerly the head of a yeshiva in Warsaw. He was a Rabbi in Notting Hill and at a Chevra Torah in Kilburn, and then Rabbi at various synagogues, including Princelet Street, Maidman Street, and Kehilas Yaakov, Springfield Park, Upper Clapton. For many years he taught at the Yeshiva Etz Chaim, London. He conducted shiurim for congregations in the East End and other parts of London, and served as a shochet for the London Board of Shechita.
Sefer Rav HaChovel is a book on Halacha and Aggada. Rav Hachovel means a ship’s captain. Verse six in the book of Jonah, chapter 1, reads (in transliteration) “Vayikrav elav rav hachovel vayomer lo mah-lecha nirdam kum kera el-Eloheycha ulay yit’ashet ha’Elohim lanu velo noved”, which means: “The captain approached him and said to him, ‘Why do you sleep? Get up, call upon your God, perhaps that God will think about us, so that we may not perish.’
Rabbi Davidson is apparently trying to wake us up.
My copy starts with a letter from the Chief Rabbi, Dr. Israel Brodie, which is pasted in to the inside cover and several pages of interesting thanks and introductions. There are very impressive haskomos (approbations), including Rabbi Isaac Herzog, Chief Rabbi of Israel, Rabbi Isaac Piekarski of South Hackney, Rabbi Samuel Joseph Rabinow of Stamford Hill and Rabbi Abraham Mordechai Hirschberg of Chicago. At the end is an interesting list of prenumeranten – prepaid subscribers, who paid the printing costs.
Jewish Miscellanies 
When was he rov in notting hill? Which shul?
In the very small print at the bottom of the first scan (perhaps too small to see) Rabbi Davidson writes that he was Rosh Yeshiva in Warsaw in Pave Street in the days of his youth and in London he was Rabbi of the synagogue in Notting Hill followed by a list of other synagogues. As Notting Hill is first, it is presumably his first appointment when he came to London. He was born in 1874. I believe that Notting Hill (Federation) was founded in 1900, but it has no rabbi listed in Ohalei Shem (1912). I found Rabbi Davidson in the 1939 Register in South Tottenham, so it is earlier than 1939. So the possible window is 1900 – 1939, and probably after 1912.
Was he Cyril Davidson’s father and therefore a mechutan of Rabbi Sperber?
I don’t think so. The names that I have for Rabbi Davidson’s children are: Chanah/Anne, born 1907, Abraham Solomon, born 1912, Peggy, born 1914, David, Betty and Pearl.
B”H
Cyril’s father Rabbi Davidsohn z”l-son in law of Rabbi Sperber z”l- was the rabbi in Stretham, South London.
Cyril Davidson has replied on the Facebook group Synagogues of London:
No. Jacob Leib Davidson was not related to me. My father was Rabbi Moshe (Morris) Davidson Rabbi of the South West London United Synagogue. His Mechutan was Rabbi Zvi Ferber not Sperber. My father obtained Semicha from Reb Elia Lopian at Eitz Chaim Yeshiva, Thrawl St. London.