TFPL, 2020: His baptism transcription (and scan of original page):

First name(s)           Horatio Powys
Last name               Lane
Birth year              1836
Birth date              06 Jan 1836
Baptism year            1836
Baptism date            03 Mar 1836
Father's first name(s)  Samuel
Mother's first name(s)  Catherine Jane
Parish                  St Anne, Soho
County                  Middlesex
Country                 England
Page                    468
Archive                 City of Westminster Archives Centre
Record set              Westminster Baptisms

The scan of the register adds that his abode was Greek St, and that the Off(iciating) Min(ister) was Rev T A Powys, his uncle.
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TFPL. July 2002: The following was found in the WWW from the British Library:

British Library, India Office Records: Accountant General's Records [IOR/L/AG/23/10/1 no.4500 - IOR/L/AG/23/10/19]

© 2002
The contents of this catalogue are the copyright of British Library, Oriental and India Office Collections
Rights in the Access to Archives database are the property of the Crown

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Accountant General's Records

_East India Company and India Office: records of the administration of service and family pension funds

    _Madras Military Fund

_________FILE_-_Roll of subscribers to Madras Military Fund - ref.__IOR/L/AG/23/10/1_ - date: 1808-c.1939

____________item: LANE, Horatio Powys 1836-1884 - ref.__IOR/L/AG/23/10/1 no.4960_[n.d.]
_______________|__[from Scope and Content]_Horace Powys b 18 Sep 1865
_______________|__[from Scope and Content]_Frederick William Robertson Powys b 29 May 1868, d 31 Jan 1869
_______________|__[from Scope and Content]_Maud Powys b 27 Jul 1870, m 21 Sep 1893, d 30 Apr 1932
_______________|__[from Scope and Content]_Percy Robertson Powys b 27 Nov 1872
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It looks like a note of the contributor and beneifiaries of a pension fund and seems to say that:

1. Horatio Powys Lane lived from 1836 to 1884
2. That his children were Horace, Frederick, Maud and Percy.
3. That their birth and death dates were as given,
4. That two of the kids were given the Robertson forename in honour of their mother's family.
5. All of the kids were given the Powys forename in honour of their father's maternal family.

I am using this as evidence for adding the kids in, and to confirm that Horace Powys Lane was indeed his son and also the father of Ella Hazel Powys Lane who married Leonard Stephen Barrington Simeon.
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His military career was:
2/Lt: 8 Jan 1855
Lt: 27 Aug 1858
2nd Capt: 7 Jan 1865
Capt: 17 June 1871
Major: 5 July 1872
Lt-Col: 1 Oct 1877
Brevet-Col: 1 Oct 1881
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His record in the India Office site is:

Name: Horatio Powys LANE
Event type: Biography
Start date:
Start year: 1836
End date:
End year: 1884
Biographical notes: Col, Madras Art & RA; IOR Biographical File; b 06 Jan & bap 03 Mar 1836 St Anne's,Soho,London, s of Samuel, artist, Greek Street; L/MIL/9/228/ ff.684-90 - Cadet 1853; d 09 Mar 1884 on board 'Cathay' homeward bound; m Flora Maria 07 Nov 1864 (b 27 Mar 1846, div 18 Dec 1883 ); Horace Powys b 18 Sep 1865; Frederick William Robertson Powys b 29 May 1868, d 31 Jan 1869; Maud Powys b 27 Jul 1870, m 21 Sep 1893, d 30 Apr 1932; Percy Robertson Powys b 27 Nov 1872
Transcribed by: British Library
India Office Records Reference: L/MIL/9/228 ff.684-90, L/AG/23/10/1-2  

Source name: IOR Biographical File
Source year:
Source edition:
Presidency:
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From the London Gazette:

29 Apr 1862: “To be Lieutenants. ... Horatio Powys Lane. Dated 27th August, 185S.”

24 Jan 1865: “Lieutenant Horatio Powys Lane to be Second Captain, vice Raikes. Dated 7th January, 1865.”

29 August 1871: “Royal Artillery, Second Captain Horatio Powys Lane (late Madras) to be Captain, vice W. F. Grey, deceased. Dated 20th June, 1871.”

16 July 1872: “To be Majors.—Commissions to bear date 5tb July, 1872. ... LATE MADRAS. ... Captain Horatio Powys Lane.”

24 May 1878: “Royal Artillery,  Major Horatio Powys Lane (late Madras) to be
Lieutenant-Colonel, vice Brevet Colonel J. McK. Macintyre.. Dated llth November, 1877.”

11 Oct 1881: “MEMORANDA.
The undermentioned Lieutenant-Colonels, Royal Artillery, to be Colonels in the Army. Dated 1st October, 1881 :— ... Horatio Powys Lane (late Madras).”
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And on Access to Archives:

LANE, Horatio Powys 1836-1884 IOR/L/AG/23/10/1 no.4960
Madras Army, b 6 Jan 1836, d 9 Mar 1884 on board Cathay m Flora Maria ROBERTSON 7 Nov 1864 (b 27 Mar 1846) Divorced 18 Dec 1883 Horace Powys b 18 Sep 1865 Frederick William Robertson Powys b 29 May 1868, d 31 Jan 1869 Maud Powys b 27 Jul 1870, m 21 Sep
Date: 1808 - 1939
Source: Access to Archives (A2A): not kept at The National Archives
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In his will, dated 25 August 1882 he left his estate in trust for his children, equally.  His trustees and executors were his brother Frederick, William Lilliston Land and Richard Deare Peerepoint and Col William Hall.

From Miscellanea Genealogica et Heraldica, Fourth Series, volume 1, p. 84.

On a stained glass window:

This window was placed here by his brother officers in affectionaten remembrance of Lieut: Col: Horatio Powis [sic] Lane, Royal (late madras) Artillery, who died at sea on the 9th March 1884 two days after leaving Bombay,
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At their marriage:
He was Lieut with Madras Royal Horse Artillery
He was 25 and a bachelor
She was 18 and a spinster
He lived at Bellary, India
She lived at Bellary, India
His father was Samuel Lane
Her father was James Alphinstone Robertson
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The National Archive has this divorce record:

Item details J 77/286/8459
  
Context
: quick reference
J  Records of the Supreme Court of Judicature and related courts
Division within J  Records of the Family Division and predecessors
J 77  Court for Divorce and Matrimonial Causes, later Supreme Court of Judicature: Divorce and Matrimonial Causes Files
Subseries within J 77  
J 77/286  

Record Summary
Scope and content
Divorce Court File: 8459. Appellant: Horatio Powys Lane. Respondent: Flora Maria Lane. Type: Husband's petition [hx].
Covering dates 1882
Availability Open Document, Open Description, Normal Closure before FOI Act: 30 years
Held by
The National Archives, Kew