It is understood the body of the 73-year-old - who was sentenced to 37 years in jail in 2014 for the murders of Christine Eadie and Helen Scott in 1977 - was cremated yesterday at Falkirk Crematorium.
The Daily Record reported that his body made its way in a silver Ford Mondeo estate, arriving just before 8am.
The procedure lasted less than 10 seconds and there was no sign of any mourners.
Sinclair died of pneumonia and heart disease on March 11.
He had been serving his sentence in Glenochil Prison, near Alloa.
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