A man was robbed after withdrawing money from a cash point in Stony Stratford High Street two weeks ago.
The 40-year-old victim was walking through the alleyway which runs between Ancell Road and Clarence Road at around 12.50am on Friday, October 10.
Two offenders approached him, grabbed him, and demanded his phone and cash.
He handed over the money and then saw three men running away down the alley.
The offenders were all white and about 5ft 10in. One was wearing a hooded top and the other a cap and glasses.
Anyone with information should contact Thames Valley Police on 101.
Alternatively call Crimestoppers, anonymously, on 0800 555 111 or online at crimestoppers-uk.org