It also means Aim’s select £1bn plus club is to be shorn of 20% of its five–strong membership.
Among Aim’s big boys, Sirius is currently ranked fourth with a market cap of just under £1.1bn.
Although its value has climbed more than six-fold over the past ten years, it only achieved its lofty status relatively recently.
Planning approval for its North York polyhalite project last year really saw its share price take off.
On the back of that came an impressive finance package to fund the project’s first phase and that effectively took out a huge chunk of risk for investors.
Indeed, such is the progress recently at the project Sirius is comfortably expected to nestle in the FTSE 100.
Others that soon may be eligible for £1bn club.
AIM wil be able cope without it.
By far and away it’s biggest member is online clothing firm ASOS plc (LON:ASC) and even though it is currently valued at £4.7bn there has been no indication that it will ever follow the Sirius route to the main board.
Of those bubbling under, drug developer and distributor Clinigen (LON:CLIN) looks the most likely next entrant.
Currently valued at £981mln, it is moving up rapidly. Transport group Dart PLC (LON:DTC) is worth just under £900mln and another candidate.
Main market to give Sirius another leg-up
Sirius confirmed its intention to move up in March.
It said the move would also provide a “more appropriate platform for its growth and is in keeping with the nationally significant nature of the company's project and its market capitalisation”.
Broker Yuen Low at Shore Capital expects its promotion to give it another leg-up.
As a FTSE 250 company it will attract plenty of tracker funds.
“Even inclusion in the All Share index would result in the relevant tracker funds being obligated to invest in the company.
“We believe that Sirius is already benefiting: we think that the recent sharp rise in the share price is occurring in anticipation.”
Asos (LON:ASC) £4.7bn
Fevertree (LON:FVTR) £1.9bn
Sirius Minerals (LON:SXX) £1.1bn
James Halstead (LON:JHD) £1.0bn
Clinigen (LON:CLIN) £981m
Dart (LON:DTC) is next at £890m.
*Many thanks to AJ Bell for the data