The agency stole the £8.3 million centralised buying business from Zenith Media last week following a two-way pitch.
The account was previously split between the two agencies. MediaVest handles planning for the tea giant and has done since the mid-80s. The agency's Tetley team will, from this week, assume responsibility for buying.
The account team is led by MediaVest client services director Tim Armes. Other key members of the team are group account director Elaine Seager and media strategist Jane Carroll.
Tetley, which boasts a 20.6 per cent of the UK tea market, has previously poured the majority of its media spend into television advertising, and has particularly favoured primetime slots. The company is likely to continue with this media plan.
The new centralised account combines media spend across generic Tetley tea advertising as well as work on specific Tetley tea bag ranges such as its circular or drawstring sub-brands.
According to MMS, the majority of spend - £6 million in 1998 - goes into marketing the teabags.
The decision to hand media to a single agency is part of a cost-cutting exercise by Tetley.
Tetley's creative work is handled by D'Arcy. There are no plans to review the creative side.