The elevation of St Luke's to become British Telecom's lead agency will have taken more than a few by surprise. And not just Abbott Mead Vickers BBDO, which finds itself having to work to St Luke's thinking just 21 months after it seemed to have buttoned it down successfully.
St Luke's too must have some concern that its win is more the result of a client spooked into action by a tumbling share price and rivals that have stolen conspicuous marches on it than one with a clear vision of where it is going.
What's certain is that, with the influx of so much BT business, St Luke's will have to do an awful lot of growing up very quickly. With its brand rooms, hot-desking, communal ownership and an overwhelming self-belief, the agency can sometimes let its annoying habit of taking itself much too seriously get in the way of its genuinely original and innovative ways of working.
True, St Luke's looks less like the testbed operation it was when it started and more like a permanent fixture on the UK agency scene, but there must be doubts about whether it has either the mindset or the infrastructure to service such a demanding account as BT. Its rocky relationship with BSkyB will certainly cause sceptics to ask if it can readily assimilate business of such a scale that it needs a large and dedicated agency team to handle it.
Moreover, St Luke's will have to pick its way through the internal politics of a client that is ill at ease with itself and which, if things continue going badly, could even find itself a takeover target in a few months' time.
While others such as Vodafone seem to be striding confidently ahead, BT looks slow and ponderous.
Indeed, it may conclude it can produce a better return to shareholders by dismembering itself, allowing its potentially more successful internet and mobile phone arms to split from its regulated domestic business.
As if that isn't enough, its relentless multimillion- pound advertising effort has become too familiar for its own good. This is particularly true of ET, the friendly alien, who now looks too old- fashioned to communicate the digital future which holds the key to BT's future.
So hats off to St Luke's if it has managed to reconcile all these problems and challenges to come up with a creative solution both sexy and relevant.
But it will need to stay alert. AMV has a reputation for playing the long game and its relationships with BT's upper echelons are strong and long-standing. Winning back almost the entire Sainsbury's business when nobody gave it a prayer should serve as a warning to anybody who doubts its resiliance