Aon's proposed acquisition of Willis Towers Watson (WTW) is set to undergo an in-depth probe by European Union (EU) regulators due to its complexity, sources have told Reuters.

Aon had agreed to purchase WTW in a $30bn (£22.9bn) all-share deal in March 2020.

The transaction faces a review once the European Commission’s preliminary review of the deal concludes on 21 December.

According to Reuters' sources, the process would last five months and would look to address any potential competition concerns that may arise out of such a large merger.

Aon and WTW declined to comment on these reports, but it is possible that an EU investigation could delay the merger, which was expected to be completed within the first half of 2021.

The acquisition would merge two of the world’s largest insurance brokers and form the UK’s largest pension consulting firm.

The firms had initially been in discussions in early 2019 about a possible acquisition, but Aon pulled out of the talks on 6 March 2019 after news of the discussions became public.

Under the purchase agreement, existing Aon shareholders would own approximately 63 per cent and existing WTW shareholders would own around 37 per cent of the combined firm.

WTW shareholders would receive 1.08 Aon shares for each WTW share, which represents a 16.2 per cent premium to WTW's closing share price on 6 March 2020.

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