If you’re looking for exceptional growth among the country’s largest accountancy firms, it won’t be the Big Four that catch your eye. No, you need to travel a little further down our Top 50 list to the number six slot where BDO Stoy Hayward reveals growth of 23.7%.

That’s well above anything the Big Four can muster and speaks volumes about where the action is in the accountancy sector. Two trends are clearly emerging ­ the capitalising on the sensitivity surrounding compliance with new regulation and a rush to make acquisitions and mergers.

In the first case, big companies are having to turn their backs on Big Four auditors to look elsewhere for tax planning, corporate finance, consultancy and advisory services.

The misfortune of the Big Four is good news for the mid-tier, as the figures show. The number five firm, Grant Thornton, reveals healthy growth of 7.3%, but, significantly, Tenon has growth of 10% and profits up 49%. Robson Rhodes is performing even better, with turnover up 14%. Haines Watts is up 12%, while our estimated figures show that Vantis could be up by as much as 25%.

The boon in advice on regulation came after the introduction of the operating and financial review, a modified combined code on corporate governance and, for those with a US listing, managing the minefield presented by the Sarbanes-Oxley Act.

Many speculate that the move to use the mid-tier to duck conflicts of interest could create its own momentum, to such an extent that these firms are considered viable alternatives to the Big Four in their own right.

Stoy’s work as auditors and reporting accountants for the £5bn flotation of PartyGaming, the online gambling site, appears to point to this as a possibility. More evidence can be seen in Grant Thornton’s aggressive new marketing campaign inviting potential clients to ‘Think beyond convention. Think beyond the Big Four.’

But the mid-tier’s performance is also linked to acquisitions. Figures for both Vantis and Stoy reflect revenue benefits expected from their split of Numerica, but other mid-tier operators have been on shopping sprees.

Tenon’s figures will benefit from the acquisition of a new office in Rochdale and tax specialists Premier Strategies. Robson Rhodes should be seeing the fruits of acquiring RSM Moffat, a specialist IT company. The whopping 38% increase in the turnover of Bentley Jennison is accounted for by the acquisitions of WBS in Leeds and Moore Stephens in Birmingham.

While a host of smaller acquisitions may make a difference, the sector is alive with gossip that a big takeover is now long overdue. A quick glance is enough to see which firms might be likely targets for those doing well.

The big question for the mid-tier is whether the trends identified here have the potential to bring about real structural change among the largest firms. Will another firm emerge to compete with the Big Four? A big takeover or merger might help hasten that possibility, but it’s still too early to tell from these figures. The next year could make all the difference.