The appointment is the latest high-profile effort by Pope Francis to shake up the Vatican since he was elected to succeed Pope Benedict last year.
The Jesuit pope has made reform of the Vatican institutions, which have been tarnished by decades of corruption and scandal, the centrepiece of his papacy.
The Vatican is expected to unveil a wide-ranging series of reforms later on Wednesday to restructure the city state's bank and its financial institutions.
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Jean-Baptiste de Franssu, former head of Invesco Europe, is expected to be confirmed as new chairman of the Vatican bank, which will be radically shaken up and its powers shrunk.
"This is an important and challenging part-time assignment over the next year," Lord Pattern said. "I'm looking forward to beginning work in late September."
Lord Patten, a leading British Catholic, stepped down from the BBC Trust in the spring on health grounds and underwent heart surgery but he is easing himself back into work.
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The Oxford university chancellor said the exact remit of his Vatican media committee would become clearer after its members met in the autumn.
Lord Patten said the committee would look especially at developing a digital strategy and ways for the church to speak to an audience beyond practising members of the faith.
Lord Patten recently waded into the heated debate about the former British colony Hong Kong and the territory's relationship with Beijing by accusing China of trying to undermine judicial independence in the global financial centre.
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