How long from flight arrival to train travel at Heathrow T2

How long should I allow for, to clear Passport control and baggage reclaim ?

Very difficult to predict, but it also doesn't matter.

Assuming you are going into London, you have three options: Heathrow Express, TFL (formerly known as Heathrow Connect) and the Piccadilly Underground Line.

None of these require you to pick a departure time up front. The Heathrow Express tickets are "anytime" (on a given day) and TFL and Tube are part of London's transit system using the Oyster Card: You scan your card when you board the train/tube and then again when exit and the fare will be calculated on the fly and deducted from your balance on the card. This is super convenient and works for any public transport in London. I highly recommend to get one.

I also recommend taking the TFL: it's less than half the price of the Heathrow Express, takes just 10 minutes longer and it also includes subsequent tube or bus rides in London. Both trains go every half hour. Depending on where you are going it may actually be faster, since you don't need to ride all the way into Paddington.

While you can pre-buy a Heathrow express ticket, there is really no need for it. There are machines everywhere and it's hard to avoid the human ticket vendors. They are pushing hard to sell you a Heathrow Express ticket, since it's so much more expensive.

Hi all thanks for your answers

The timing does matter, I should have mentioned that I have an onward train Journey from Kings Cross to Newcastle while I realise I don't need a timed departure from Terminal 2 I do have to catch a specific train at Kings cross as flexi or buying on the day was looking like too much of an expensive option for me.

A friend of mine did this journey last week and she's jist told me that she got there (kings cross) within 2 hours at the same time of day

On the basis of this and your helpful answers I have left three hours between landing and my train departure from Kings Cross

I intend to use the underground if I get through T2 at reasonable speed, but get the express if it's looking tight and timing permits.

To keep this flexible I just booked London King's cross to Newcastle and not bundled Heathrow to London ticket with it.

Update:

made the train successfully

From touchdown to disembarking and joining the border control queue was 15 mins. .note that some (all?) Airlines are disembarking passengers in blocks of seats due to social distancing, and not lettimg the next lot to move until the first lot have cleared the plane. If you are near the back as i was, and the plane only has stairs or an airbridge at the front, this can really delay your disembarkation.

All e-gates were shut down and everyone was being processed manually. It took about 1:15 to get through and a further 15 nins to get to the underground station, which included a detour to the WC after having to wait for so long

Train into kings cross was about an hour.

Cheers

Glen