John Morgan has corrected an error in that his second name was not Percy (as my grandfather wrote) but Peter.

There is no birth record on FreeBMD for the decade either side of his reported birth.  Nor any marriage record - but there was a Notice in the Shields daily Gazette.  See also the appended extract from the South African DNB.
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His death index:

First name(s)  Edward P
Last name      Mathers
Gender         Male
Birth year     1850
Age            74
Death quarter  4
Death year     1924
District       Kensington
County         London
Volume         1A
Page           174
Country        England
Record set     England & Wales Deaths 1837-2007
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His probate index:

1924
MATHERS Edward Peter of 10 Stanley-crescent Notting Hill Gate Middlesex and of 83 Bishopsgate London died 13 October 1924 at 10 Stanley-crescent  Probate London 21 November to Mary Augusta Mathers widow.  Effects £9125 11s. 3d.
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Later on I could order his will to see what it says of their children.

But this will wait until I get a bit further down the Powys of Lilford tree.
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On his gravestone in :

        EDWARD PETERS MATHERS
         BELOVED HUSBAND OF
            MARY MATHERS
      DIED 13TH PF OCTOBER 1924
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Also nearby:

Relationships on the headstone
add
Janet Mathers (Young)
Buried here
Not Available - 12 Apr 1900

Mary Mathers
Buried here
Not Available - Not Available

David Mathers
Buried here
Not Available - 15 Jan 1873

Henry George Mathers
Buried here
Not Available - 30 Mar 1861

Helen Duff Mathers
Buried here
Not Available - 31 Jul 1867
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from the Billion Graves site at <https://billiongraves.com/grave/Edward-Peter-Mathers/30747100>;
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The Scottish Genealogical Society has transcribed this memorial in Grange Cemetery, Edinburgh, Midlothian:

“Sacred to the memory of David MATHERS who died 15th January 1873 aged 59; and of his wife Janet YOUNG who died 13th April 1900 aged 77.Edward Peter MATHERS, beloved husband of Mary MATHERS, died 13th October 1924; and to the beautiful ever - living memory of Mary MATHERS.M 61. also of their children - Henry George who died 30th March 1861 aged 4; and Helen Duff who died 31st July 1867 aged 14; William Young who died 19th January 1909 aged 60“
___________________________________

(From the South African DNB)

Founded & edited The Natal Advertiser; corresp. for the Natal Mercury
during the Zulu War 1879 & First Anglo-Boer War 1880-81; sent reports
to The Scotsman & various London papers; "was special commissioner for
the Mercury 1883-84 when he accompanied a party of explorers travelling
through the little-known and fever-infested region from Delagoa Bay to
the De Kaap Goldfields; Became convinced that SA was richest goldfield
land on earth & expressed this in stream of letters, reports & articles
to press; wrote books A Glimpse of the Goldfields 1884 and The
Goldfields Revisited 1887, & South Africa, and how to reach it 1889;
returned to UK in 1888 and founded & edited a weekly journal South
Africa; in 1890s he visited Matabeleland and Mashonaland, which led to
book Zambesia: England's Eldorado in Africa (1892); fact-finding
missions to Egypt and Sudan in 1893; 1896 reported from SA on The
Reform Trial, and the Jameson Raid; narrowly missed siege of Ladysmith
(02.11.99-28.02.1900); returned to UK during 2nd Boer War in Feb 1900;
1903 to N America - opened a South Africa office on Broadway, did
interview in 1904 with Theo Roosevelt; back to SA in 1904, issued maps
of SA and Atlas of the Rand - still v keen on gold developts; staunch
imperialist; director of the Swaziland Corporation; member of the Royal
Geographical Society, Royal Colonial Institute, Fellow of the Royal
Geographical Society.

A notice of their marriage is to be found in the Shields Daily Gazette of Fri 2nd Oct 1885”

“Marriage: Mathers - Powys--At St Cyprian’s Church Durban, Natal, on August 6th, by the Rev R S Kendall, Edward P Mathers (late of Edinburgh), Editor of the Natal “Advertiser”, to Mary Augusta,, eldest daughter of R H Powys (late of London and Madras), and granddaughter of the late Captain the Hon R V Powys, Bengal Army”

(What a lot of succulent detail!)

And from Edinburgh Evening News of 23 Sep 1885:

“                          MARRIAGE
“  At St Cyprian’s Church, Durban, Natal, South Africa, on the 6th August, by the Rev R. S. Kendall, Edward P Mathers, younger son of the late David Mathers, of Edinburgh, to Mary Augusta, eldest daughter of Robert Horace Powys, of Durban, late of Madras.”
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Family Search has this transcript of their marriage:

Name:                             Edward Peter Mather
Event Type:                       Marriage
Event Date:                       06 Aug 1885
Event Place:                      Durban, Natal, South Africa
Gender:                           Male
Age:                              34
Birth Year (Estimated):           1851
Spouse's Name:                    Mary Augusta Powys
Spouse's Gender:                  Female
Spouse's Age:                     25
Spouse's Birth Year (Estimated):  1860
Reference ID:                     262 , GS Film number: 1259172 , Digital Folder Number: 004236415 ,
                                  Image Number: 00093
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