A man was knocked unconscious in an alley in Caddington during an attempted robbery on Sunday evening.
Police are linking it to a robbery involving two school children in Caddington three days earlier and are appealing for witnesses.
The male victim had left the Cricketers Arms at about 6.30pm on Sunday when he was approached by a man in the alley leading to Crosslands.
The man demanded he hand over his wallet but the victim refused and punched him.
A second would-be robber then attacked him from behind, hitting him round the head and leaving him unconscious on the floor.
They fled the scene empty-handed and the victim regained consciousness and was taken to the Luton & Dunstable Hospital.
On Thursday, two Manshead School students were approached by a group of three men who demanded money in Dunstable Road between 4.20pm and 6pm.
The boy was punched and knocked out and the offenders stole his phone.
The girl was pinned against a wall and searched for property.
Call Det Con Tom Hamm on 01582 394498 with information.