Help! Have I got Japenese Knotweed growing in my garden?

I have had a couple of friends come round recently and suggest that I might have Japenese knotweed in my garden - I didn't even know what it was. I have looked online and there are lots of things that I have read and seen that suggest it isn't, but, it does have a hollow stem and grows quite high!

I have attached a picture and would be greatful if anyone can identify what it actually is!

False alarm I think.

looks more like himalayan balsam to me.  I've never had it myself so no idea how to get rid of it but whatever you do don't let it seed.  It seeds itself by a sort of explosion to scatter the seed all over the place, probably best to cut off all the flowers, crush the leaves slightly and apply Roundup, but I'm happy to be corrected.

Yes, Himalayan Balsam.  Pull it up BEFORE IT SEEDS, put it in a bin bag with some water, let it rot down and take it to the tip.  The seeds are catapulted high and for yards and yards, so it's likely that one of your neighbours has a plant.

 At our last address a next door neighboour sowed a few seeds.  The flowers looked lovely and the bees loved it, he said.  The following year we had seedlings springing up all over the place.  They're pretty easy to identify even when they're quite small so we just made sure we pulled everyone we saw up and destroyed it.  If you pull it and leave it on the soil it will re-root!

 Within 3 years the next door garden was totally overgrown with HB, and the tenant moved out.  The landlord mowed it down and installed a membrane and shingle.  I bet seedlings are still trying to find a way through or around the membrane.

We moved - not because of the HB, but because of the unpredictability of having ever-changing tenants next door - and to get a much bigger garden 

Yes, pretty though it is and the bees do love it, but get those flowers cut off now or you will really regret it. It has completely taken over parts of the banks of the River Dee in and above Chester. You only have to brush against the plants when they're seeding to set off the explosions, great fun but disastrous

Hi everyone

Thank you very much for all your help and advice. I'm putting a paved area in there tomorrow for a new shed so will make sure I dispose of the flowers carefully! It does explain why I have seen soo many bees recently though.

Very relieved to have it confirmed that it is not anything more severe!