TFPL, August 2003:

In the Royal Engineers Roll his regimental promotion history is:
1804, 1st November: 2nd Lieut
1805, 1st March: Lieut
1810, 10th July: 2nd Capt
1814, 16th May: Captain
1829, 26th December: Lt-Col
1846, 1st April: Colonel

Note that his name was spelt without a 'p', which 'p' was in the various Hallifax records.

His war service was in Holland in 1813-15.  In his will he refers to a medal and clasp that he was awarded in General Orders on 1st June 1847.

He is reported to have died at Dover on 13th July 1851.
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His will has been found at the PRO and is ordered.
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TFPL, later in August, 2003:
See the Will notes for details of his family.
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TFPL, Sept 2003:
In the photo of the St James' Dover marriage register, he gave his parish as St Andrews, Edinburgh.  This indicates that he was a Scotsman.

This makes it more likely that the second name of his third son of Forsyth came from his side of the family and might even have been his mother's.  But for Scotland I have seen a report that Thomson is the seventh most common name there, and about the twentieth in England.  So it will be needle in haystack time to find his parents.
He should be on the 1851 census for Dover, if only we knew where he lived at that time.  This may give his place of birth and will give his approx age.
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On his death certificate it says he died at 1 Wellington Place, Dover, where George Payne also lived and was the informant.  Robt died of Bronchities which he had had for 14 days and exhaustion for 4 days.  He was 65 at death.  His death certificate is the earliest document that I have found that spelt his surname with ‘p’.

In the 1851 census, thanks to Jane Nantais, he was living with his son Frederick at 1 Wellington Place which was a lodging house; he was 64, a col in Royal Engineers and born in Scotland.  George Payne was there too, apparently the husband of the sister of the lodging house keeper.

In the 1841 census, again thanks to Jane, he was at Dover, in the Army and with his wife, two sons and two grand-daughters, with two servants.  The address was, roughly, Arch Cliff Fort M H.  George and Frederick were both down as aged 20: were they twins?
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TFPL, May 2016: Thanks to some information from Terry Mason, his parents marriage was found in 1781.  But no record of any baptsim in Scotland on the Old parish registers, so there is no categoric evidence of his parentage.

However FamilySearch has come up trumps with this index record:

Name Robert Thompson
Gender Male
Christening Place EDINBURGH PARISH, EDINBURGH, MIDLOTHIAN, SCOTLAND
Birth Date 23 May 1786
Birthplace Edinburgh Parish, Edinburgh, Midlothian, Scotland
Father's Name George Thompson
Mother's Name Katharine Millar

(I cannot praise enough the Scots practice of including the mother’s maiden names.)

Though note the erroneous spelling of his surname with the inclusion of the ‘p’.
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He and Harriet had two further children who appear in no records.  Terry Mason has found a report the the following died on a boat taking them to South Africe:

Latham Augustus Thomson born around 1822, died
Charlotte Augusta born around 1824,

The best report he found was:

“On board the Belzoni, on her passage to the Cape, died of fever, August 15th – Latham Augustus aged 8 years – August 16th, Charlotte Augusta aged 6 years and August 23rd, Laetitia aged 16 years… the children of Lt. Col. Thomson, Royal Engineers.”

Letitia had been baptised in Dover in 1814,  The last one to be baptised in Dover was Alfred Taddy Thomson.

The next known birth was Frederick Forsyth Thomson who consistently reported in the censuses that he was born in Sheerness, Kent c. 1821.

It is conceivable that the two following briths were also at Sheerness.  The trouble is that there was no church there then, not until 1836.  I have seen reports that Sheerness was served from Minster, Sheppy but there is nothing on that register either.  Maybe that great genealogical tool, years of time, will permit the records to be found and to appear on the internet.
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In his will, dated 20th September 1850, he lists:
His late wife (un-named), buried in grave no 8002 in Kensal (?) Green,
His late mother-in-law, Mrs Latham,
His brother-in-law, Samuel Metcalfe Latham (first executor),
His (probable) sister-in-law, Miss Eliza Latham (second executor),
His son, Frederick Forsyth Thomson,
His daughter Mrs Harriet Hallifax,
His son George Latham Thomson,
His father (unnamed),
His son Alred Taddy Thomson.

His four children were listed in the order:
Harriet
Geo
Alfred
Fred
so this is probably their birth order.

Admon was on 26th July 1851.
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At their marriage, her brother-in-law Rev John Taddy officiated and the witnesses were Sam Latham and a Wm (illegible).  Her and Robert's signatures are on the photo of the register.

The LDS transcription:

Name Robert Thomson
Spouse's Name Harriet Latham
Event Date 28 Mar 1811
Event Place Saint James The Apostle,Dover,Kent,England

Indexing Project (Batch) Number: M03655-1
System Origin England-ODM
GS Film number 355636
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