Burglars are thought to have scoped-out a target house three times before a £15,000 break-in.
A family told police of a series of unusual calls at their home in Redford Avenue, Coulsdon, in the five days before it was burgled on Wednesday, November 14.
A caller came to the house and asked for David and Matt and said he thought it was a friend's house, two days later another caller came to ask if they wanted some fireworks and on Tuesday, November 13, the day before the break-in, a third caller asked if the black Audi in the drive was for sale.
The house was burgled at around 4pm the following day. Cash, bank cards, passports and jewellery were stolen - the total value of the haul was £15,600.
PC Duncan Harris believes the callers may have been visiting the property to see if it was occupied.
He said: "If anyone calls at your home with enquiries that seem so odd or unusual that they make you suspicious, then close the door on them, make a note of their description and any vehicle registration number, and call police immediately on 999.
"Put simply, if it doesn’t look right or feel right, then call police."
The callers were all white men. One was between 20 and 30-years-old and wore dark clothing and a beany hat, another was 24 to 25-years old, 6ft tall, wore a white shirt and dark trousers and spoke with a Welsh or Scottish accent and the third was about 30-years-old, about 5ft 5in tall and wore dark clothing with a baseball hat.
If you have information you can call Sutton's burglary and robbery investigation team on 0208 649 0777 or the charity Crimestoppers on 0800 555 111.