Though the deaths index on FreeBMD only shows a middle initial of R, the GRO online index has his full middle name as Robert and has the option of ordering a digital image from the death register for £2.50.
https://www.gro.gov.uk/gro/content/certificates/Death Notice
Newcastle Evening Chronicle
03 October 1936, page 2, col 1
Callender - Fence Houses, Greenbank House, Woodstone Village, 2nd instant, 79 years, William Robert, beloved husband of Isabella Callender (nee Edwards). Interment Lumley Churchyard; cortege laving residence 2 pm Tuesday. Friends please accept this (the only) intimation.
Probate Calendar 1936
CALLENDER William Robert of Greenbank House Woodstone Village, Fence Houses County Durham died 2nd October 1936 Administration (with Will) Durham 10 December to George Callender foreman bricklayer and Jane Newson (wife of John Newson). Effects £3322 13s 9d
(can order a copy will and grant for £1.50 from.
https://probatesearch.service.gov.uk/#wills )
In Memoriam Notice
Sunderland Daily Echo and Shipping Gazette
02 October 1937, page 8, col 1
CALLENDER - In loving memory of my dear husband, William Robert, who died October 2 1936.
God saw the road was getting rough,
The hill too hard to climb;
He gently took him by the hand,
And whispered, "Peace be thine.'
- Ever remembered by his loving wife.
Boo