Ask an Property Solicitor. Get an Answer ASAP.
You may be liable for capital gains tax. Please use the following link for further guidance and also use their online calculation to see if you are liable to pay Capital Gains Tax;
Further information - https://www.gov.uk/tax-sell-property
Calculator - https://www.gov.uk/tax-sell-property/work-out-your-gain. If you do need to pay capital gains tax, I would also advise to consult an accountant immediately.
I hope this helps and please leave positive feedback. If I can assist with anything else, please do let me know.