The fast of 10th Teves (when it falls on erev Shabbos)

This is the day that Nevuchadnezar laid siege to Yerushalayim[1] and marks the beginning of the Churban. It also follows the day that Ezra Hasofer died and takes place two days after the Torah was forcibly translated into Greek by King Ptolemy[2],  which resulted in a distortion of the intended meaning of the Torah[3]. The significance of the Fast is such that if it were it to fall on Shabbos we would fast even then[4].

[1] Rambam, Taniyos 5:2

[2] Shulchan Aruch, O.C., 580:2

[3] Toras Moshe (Chasam Sofer), Devarim, Drashah for 8^th Teves

[4] Abudraham, Hil. Taanis

From alos ha’shachar (dawn), which is at 6:13am this year in London.

The fast finishes at nacht (halachic nightfall) which is 5:01pm this year in London.

No. The fast concludes at nightfall, regardless of what time you light Shabbos candles or daven maariv and one must wait until this time before starting kiddush[1].

Sholom Aleichim and Eishes Chayis may be said before this time and generally by the time one has returned from shul and said these, the time for kiddush will have already arrived.

[1] Rema, O.C., 249:4

Tachanun and Ovinu Malkeinu[1] are said at shacharis but are omitted at mincha[2].

Just like on a regular fast day, kriyas hatorah and “aneinu” are said at both at shacharis and mincha, even if the minyan was not able to start until after shkiyah[3].

Kiddush is not recited in shul as the fast will generally not have ended by the time the community reach this point.

[1] Teshuvos Dvar Yehoshua iii, YD, 63

[2] See Mishnah Berurah 422:3

[3] Mishnah Berurah 550:11

Generally, on a fast day, a בעל נפש (a punctilious individual) should be stringent not to bathe on a fast day. However, since this fast is on Friday, one should bathe due to כבוד שבת[1]. It is also permitted to shave.

[1] Mishnah Berurah 550:6

Although brushing teeth (and using mouthwash) should generally be avoided on a fast day[1], if one would experience notable discomfort on either Friday or Shabbos by not brushing their teeth it is permitted[2].

[1] See Shulchan Aruch, O.C. 567:3

[2] Teshuvos Minchas Yitzchak iv:109

This is permitted if one tastes it in their mouth and spits it out afterwards, taking great care not to swallow the food/soup[1].

[1] Mishnah Berurah 567:6, Shmiras Shabbos K’Hilchesa 42:61