Laura,
This is a very intriguing set of circumstances but I think it wise to ignore the 1881 Census return at Litcham for now as it contains too many anomalies; the family unit was new to that parish; and the following records are extant:
Bridgham St Mary Baptism
No 526 24 May 1873 Albert son of Albert & Harriett MALLOWS Labourer
No 526 24 May 1874 Albert son of ditto [source appears to be PR Transcript of above record and a year 1874 baptism is more relevant to a 4Q 1873 Birth reg'n. ]
GRO Birth refs which include Bridgham in the Registration District:
4Q 1873 Albert MALLOWS Guiltcross 4b 226
3Q 1875 Alice MALLOWS Guiltcross 4b 235
It appears that 4Q 1857 Robert MALLOWS married Harriett CLEARS ref: Guiltcross 4b 652
Bridgham St Mary Marriage [FreeReg transcript]
25 Dec 1857 Robert MALLOWS ofa Widr son of Robt = Harriett MEARS sic ofa spin dau of Robt, thatcher
Witnesses: John DARLEY; Mary Ann SAYERS
The bride's surname is CLEARS in the GRO index and in 1841 she is recorded CLEARES aged 20 with father Robert, a thatcher, and family at Market Weston, Suffolk, the birthplace she records throughout her marriage to Robert MALLOWS. 1851 Harriet CLEARES is at home recorded aged 30. She died in 1888 at Kenninghall, Norfolk but Administration was not granted until 1893 to husband Robert MALLOWS, labourer. Effects £132.
It appears likely that Robert's 1st wife, Rebecca, was mother to Wm c1847; Robt c1850; Albert c1852 & Rebecca c1857:
Burial at Bridgham St Mary’s
22 Mar 1857 Rebecca MALLOWS 32
It did not escape my notice that in 1871 Alfred HARRIS & family shared accommodation at Limehouse with a John CLARK, Travelling Auctioneer, and wife Esther with son John Percy 9 mos. Is it not too much of a coincidence that a John Hawkins CLARK, Travelling Auctioneer, featured in Tonbridge Petty Sessions in August 1880? Kent & Sussex Courier - Friday 03 September 1880
Finally, do you have the name of the fourth surviving child of Isabel's eight from her marriage to CLARKE, as indicated in her 1911 return? I'm aware of Frank, Ernest and Alfred but the 4th eludes me and there are too many permutations for easy elimination. As she had no children with MALLOWS, have you considered that any child responsible for her burial arrangements might have registered her death as CLARK/CLARKE?
dee-jay