Police want to speak to two men after an iPad was stolen on a tram between Beckenham Junction and Sandilands.
The theft took place on February 3 after a man, 20, accidentally left the iPad on a seat after getting off at Sandilands in Croydon.
Police Constable James Kirk of British Transport Police, said: "The victim boarded the tram at Beckenham Junction towards Sandilands at 11pm, getting on at the rear of the tram sitting at the left hand side of the doors in a seat facing forwards.
"When he left the tram a few minutes later at Sandilands he realised he had left his iPad, valued at £500, on the seat next to him."
Police believe the two men could have key information to help their investigation.
He added: "We have distributed these images on local police intelligence systems and have carried out local enquiries to identify the current location of the iPad.
"If you recognise either of these two men, who may be from either the Croydon or Tulse Hill area, or have any information about this incident, contact us immediately."
Anyone with information is asked to contact British Transport Police on 0800 40 50 40, or text 61016, quoting incident reference LSA/B2 of 12/03/14.
Alternatively call Crimestoppers anonymously on 0800 555 111.
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