Chelsea could be forced to give Romeu back to Barcelona in 12 months
The 19-year-old Spanish midfielder - seen as cover for the injured Michael Essien - will join his new team-mates after this month's Under 20 World Cup in Colombia.
Barcelona can re-sign Romeu for £9.5m at the end of the season after insisting on a buy-back clause - to avoid a repeat of the Cesc Fabregas saga.
Aged 16, Fabregas left the Nou Camp for nothing but will cost close to £40m to seal his return from Arsenal.
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